ALBERT

Description: ABSTRACT With the objective to understand the generation, propagation and nonlinear evolution of ion cyclotron waves (ICWs) in the corona and solar wind, we use electromagnetic hybrid (kinetic ions, fluid electrons) simulations with a non-uniform magnetic field. ICWs are generated by the temperature anisotropy of O 5+ ions as minority species in a proton-electron plasma with uniform density. A number of magnetic field models are used including radial and spiral with field strength decreasing linearly or with the square of the radial distance. O 5+ ions with perpendicular temperature larger than parallel are initially placed in the high magnetic field regions. These ions are found to expand outward along the magnetic field. Associated with this expansion, ion cyclotron waves propagating along the magnetic field are also seen to expand outward. These waves are generated at frequencies below the local gyro-frequency of O 5+ ions propagating parallel and anti-parallel to the magnetic field. Through analysis of the simulation results we demonstrate that wave generation and absorption takes place at all radial distances. Comparing the simulation results to observations of ICWs in the solar wind shows some of the observed wave characteristics may be explained by the mechanism discussed in this paper.

Description: The characteristics of nighttime medium-scale travelling ionospheric disturbance (MSTID) features observed over Yonaguni (24.5 o N, 123.0 o E; 19.3 o N dip latitude), Japan are studied using all-sky imaging of OI 630.0 nm airglow emission. The uniqueness of these observations is that the area observed by the imager covers the transition region between low to middle latitudes in the ionosphere. Typical low latitude limit of mid-latitude type nighttime MSTIDs possessing phase front alignments along the northwest to the southeast occurs in this region. These MSTID features are rarely sighted at dip latitudes below 15 o . We selected two year period for analysis in which one year corresponded to the solar minimum conditions and another year to the solar maximum conditions. The MSTIDs were observed to extend to farther lower latitudes during the solar minimum conditions than during the solar maximum periods. Their observed range of wavelengths, phase velocities, phase front alignment and propagation directions are similar to those observed at typical mid-latitude sites. However, on many occasions the phase fronts of the observed MSTIDs did not extend over the whole field of view of the imager indicating that some process inhibits their extension to further lower latitudes. Detailed investigation suggests that the poleward propagating enhancement of airglow intensity, probably associated with the midnight pressure bulge, causes the MSTID features to disappear when they reach lower latitudes later in the night. When the MSTIDs reach lower latitudes well before midnight, they are found to be inhibited by the equatorial ionization anomaly crest region.

Description: We study a magnetosphere-ionosphere coupling at low-latitudes during a moderate (CIR/HSS-driven) geomagnetic storm on 22 July 2009. Recently, it has been shown that during major (CME-driven) storms, quasi-trapped 〉30 keV electrons largely enhance below the radiation belt in the forbidden zone and produce an additional ionization in the topside ionosphere. In this work, we examine a case of the recurrent storm when the magnetosphere-ionosphere coupling through the quasi-trapped electrons also may take place. Data from NOAA/POES and Japanese GOSAT satellites were used to identify the forbidden electron enhancement (FEE). We find a positive vertical gradient of the electron fluxes that indicates to the radiation belt as a source of FEE. Using global ionospheric maps (GIM), radiotomography reconstructions from beacon data and COSMIC/FS3 radio occultation measurements, we have observed an unusually large area in the night-time ionosphere with increased total electron content (TEC) and prominent elevation of the F-layer at low-latitudes that coincides with FEEs spatially and temporarily. Ionizing particles are considered as an addition source of ionization along with generally accepted mechanisms for storm time TEC increase (a positive ionospheric storm). We discuss relative contributions of the FEE and disturbance dynamo electric field in the TEC increases during the storm recovery phase.

Description: Bursty bulk flow (BBF) events, frequently observed in the magnetotail, carry significant energy and mass from the tail region at distances that are often greater than 20 R E into the near-Earth plasma sheet at ~10 R E where the flow is slowed and/or diverted. This region at ~10 R E is referred to as the BBF braking region. A number of possible channels are available for the transfer or dissipation of energy in BBF events including adiabatic heating of particles, the propagation of Alfvén waves out of the BBF braking region and into the auroral region, diverted flow out of the braking region, and energy dissipation within the braking region itself. This study investigates the generation of intense high-frequency electric field activity observed within the braking region. When present, these intense electric fields have power above the ion cyclotron frequency and almost always contain nonlinear structures such as electron phase space holes and double layers, which are often associated with field-aligned currents. A hypothesis in which the observed high-frequency electric field activity is generated by field-aligned currents resulting from turbulence in the BBF braking region is considered. Although linear Alfvén waves can generate field-aligned currents, based on theoretical calculations, the required currents are likely not the result of linear waves. Observations from the THEMIS satellites support the picture of a turbulent plasma leading to the generation of nonlinear kinetic structures. This work provides a possible mechanism for energy dissipation in turbulent plasmas.

Description: Dipolarization fronts (DFs) are often associated with the leading edge of Earthward bursty bulk flows in the magnetotail plasma sheet. Here multi-spacecraft THEMIS observations are used to show that a spatially limited region of counter-propagating ion beams, whose existence is not evident in either the plasma moments or the electric field, is observed on the low density side of DFs. The THEMIS magnetic field data are used to establish appropriate comparison cuts through a particle-in-cell (PIC) simulation of reconnection, and very good agreement is found between the observed and simulated ion distributions on both sides of the DF. Self-consistent back-tracing shows that the ion beams originate from the thermal component of the pre-existing high density plasma into which the DF is propagating; they do not originate from the inflow region in the traditional sense. Forward tracing shows that some of these ions can subsequently overtake the DF and pass back into the high density pre-existing plasma sheet with an order-of-magnitude increase in energy; this process is distinct from other ion reflection processes that occur directly at the DF. The interaction of the reconnection jet with the pre-existing plasma sheet therefore occurs over a macroscopic region, rather than simply being limited to the thin DF interface. A more general consequence of this study is the conclusion that reconnection jets are not simply fed by plasma inflow across the separatrices, but are also fed by plasma from the region into which the jet is propagating; the implications of this finding are discussed.

Description: Low energy (1-10 MeV) neutrons emanating from the Sun provide unique information about accelerated ions with steep energy spectra that may be produced in weak solar flares. However, observation of these solar neutrons can only be made in the inner heliosphere where measurement is difficult due to high background rates from neutrons produced by energetic ions interacting in the spacecraft. These ions can be from solar energetic particle events or produced in passing shocks associated with fast coronal mass ejections. Therefore, it is of the utmost importance that investigators rule out these secondary neutrons before making claims about detecting neutrons from the Sun. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging ( tect MESSENGER ) Neutron Spectrometer recorded an hour-long neutron transient beginning at 15:45 UTC on 2011 June 4 for which [13] claim there is “strong evidence" that the neutrons were produced by the interaction of ions in the solar atmosphere. We studied this event in detail using data from the MESSENGER neutron spectrometer, gamma-ray spectrometer, X-ray Spectrometer, and Energetic Particle Spectrometer, and from the particle spectrometers on STEREO A . We demonstrate that the transient neutrons were secondaries produced by energetic ions, probably accelerated by a passing shock, that interacted in the spacecraft. We also identify significant faults with the authors’ arguments in favor of a solar neutron origin for the transient.

Description: The response of the D-region low latitude ionosphere has been examined for extreme space weather event of 14-16 December 2006 associated with a X1.5 solar flare and an intense geomagnetic storm ( Dst  = -146 nT) using VLF signals from NWC (19.8 kHz) and NPM (21.4 kHz) transmitters monitored at Suva (Geog. 18.10 ο S, 178.40 ο E), Fiji. Modeling of flare associated amplitude and phase enhancements of NWC (3.6 dB, 223 o ) and NPM (5 dB, 153 o ) using Long Wave Propagation Capability code shows reduction in the D-region reflection height ( H ') by 11.1 km and 9.4 km, and enhancement in ionization gradients described by increases in the exponential sharpness factor ( β ) by 0.122 and 0.126 km -1 , for the NWC and NPM paths, respectively. During the storm the daytime signal strengths of the NWC and NPM signals were reduced by 3.2 dB on 15 and 16 December (for about 46 hrs) and recovered by 17 December. Modelling for the NWC path shows that storm-time values of H ' and β were reduced by 1.2 km and 0.06 km -1 , respectively. Morlet wavelet analysis of signals amplitudes shows no clearly strong signatures of gravity wave propagation to low latitudes during the main and recovery phases. The reduction in VLF signal strength is due to increased signal attenuation and absorption by the Earth-ionosphere waveguide due to storm-induced D-region ionization changes and hence changes in D-region parameters. The long duration of the storm effect results from the slow diffusion of changed composition/ionization at D-region altitudes compared with higher altitudes in the ionosphere.

Description: We study the ion density and temperature in the pre- and post-dipolarization plasma sheets in the Earth's magnetotail, using 9 years (2001–2009) of Cluster data. For our study we selected cases when Cluster observed dipolarization fronts (DFs) with an earthward plasma flow greater than 150 km/s. We perform a statistical study of the temperature and density variations during the DF crossings. Earlier studies concluded that on average the temperature increases while the densitydecreases across the DF. Our statistical results show a more diverse picture: While ~53% of the DFs follow this pattern (category A), for ~28% the temperature decreases while the density increases across the DF (category B). We found an overall decrease in thermal pressure for category A DFs with a more pronounced decrease at the DF duskside, while DFs of the category B showed no clear pattern in the pressure change. Both categories are associated with earthward plasma flows, but with some difference: (1) Category A flows are faster than category B flows. (2) The observations indicate that category B flows are directed perpendicular to the current in the near-Earth current sheet while category A flows are tilted slightly duskward from this direction. (3) The background B z of category B is higher than that of category A. Based on these results we hypothesize that after reconnection takes place, a BBF emerges with category A characteristics, and as it travels earthward it further evolves into category B characteristics, which is in a more dipolarized region with slower plasma flow (closer to the flow braking region).

Description: Santín et al. (2014) report the conversion of different boreal forest biomass pools to pyrogenic organic matter (PyOM) during a forest fire, and suggest that ~100 Tg C y −1 may be converted to PyOM in boreal forests globally. They further suggest that PyOM formation represents a missing C sink. The phrase ‘missing C sink’ derives from a lack of closure in the atmospheric C budget. Approximately ⅓ of the CO 2 emitted to the atmosphere via burning of fossil fuels and land use change cannot be accounted for after oceanic uptake and atmospheric accumulations are tallied (Schlesinger and Bernhardt 2013). This article is protected by copyright. All rights reserved.

Description: Tree-ring analysis is often used to assess long-term trends in tree growth. A variety of growth-trend detection methods (GDMs) exist to disentangle age/size trends in growth from long-term growth changes. However, these detrending methods strongly differ in approach, with possible implications for their output. Here we critically evaluate the consistency, sensitivity, reliability and accuracy of four most widely used GDMs: Conservative Detrending applies mathematical functions to correct for decreasing ring-widths with age; Basal Area Correction transforms diameter into basal-area growth; Regional Curve Standardization detrends individual tree-ring series using average age/size trends; and Size Class Isolation calculates growth trends within separate size classes. First, we evaluated whether these GDMs produce consistent results applied to an empirical tree-ring dataset of Melia azedarach , a tropical tree species from Thailand. Three GDMs yielded similar results – a growth decline over time – but the widely used Conservative Detrending method did not detect any change. Second, we assessed the sensitivity (probability of correct growth trend detection), reliability (1- probability of detecting false trends), and accuracy (whether the strength of imposed trends is correctly detected) of these GDMs, by applying them to simulated growth trajectories with different imposed trends: no trend, strong trends (-6% and +6% change per decade), and weak trends (-2%, +2%). All methods except Conservative Detrending, showed high sensitivity, reliability and accuracy to detect strong imposed trends. However, these were considerably lower in the weak or no-trend scenarios. Basal Area Correction showed good sensitivity and accuracy, but low reliability, indicating uncertainty of trend-detection using this method. Our study reveals that the choice of GDM influences results of growth-trend studies. We recommend applying multiple methods when analysing trends and encourage performing sensitivity and reliability analysis. Finally, we recommend Size Class Isolation and Regional Curve Standardization, as these methods showed highest reliability to detect long-term growth trends. This article is protected by copyright. All rights reserved.

Description: (http://onlinelibrary.wiley.com/doi/10.1111/gcb.12697/full) The above article, published online on 18 August 2014 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, Dr Melanie Harsch and Associate Professor Janneke Hille Ris Lambers, journal Editor‐in‐Chief, Professor Stephen Long, and John Wiley & Sons Ltd. The retraction has been agreed for the following reasons: a coding error affected the results and therefore invalidated the broad‐scale conclusions presented in the article. The article presented broad‐scale patterns of species distribution shifts in response to recent climate change. Unfortunately, it has since been found that one approach used to account for sampling bias, the null model approach, was affected by the coding error. Following the identification of the coding error, we are therefore retracting the article. We thank Drs Adam Wolf and William Anderegg for bringing this issue to our attention. Reference Harsch MA, Hille Ris Lambers J (2014) Species distributions shift downward across western North America. Global Change Biology. doi: 10.1111/gcb.12697.

Description: Marine organisms are simultaneously exposed to anthropogenic stressors with likely interactive effects, including synergisms in which the combined effects of multiple stressors are greater than the sum of individual effects. Early life stages of marine organisms are potentially vulnerable to the stressors associated with global change, but identifying general patterns across studies, species and response variables is challenging. This review represents the first meta-analysis of multi-stressor studies to target early marine life stages (embryo to larvae), particularly between temperature, salinity and pH as these are the best studied. Knowledge gaps in research on multiple abiotic stressors and early life stages are also identified. The meta-analysis yielded several key results: 1) Synergistic interactions (65% of individual tests) are more common than additive (17%) or antagonistic (17%) interactions. 2) Larvae are generally more vulnerable than embryos to thermal and pH stress. 3) Survival is more likely than sub-lethal responses to be affected by thermal, salinity, and pH stress. 4) Interaction types vary among stressors, ontogenetic stages, and biological responses, but they are more consistent among phyla. 5) Ocean acidification is a greater stressor for calcifying than non-calcifying larvae. Although more ecologically realistic than single-factor studies, multifactorial studies may still oversimplify complex systems, and so meta-analyses of the data from them must be cautiously interpreted with regard to extrapolation to field conditions. Nonetheless our results identify taxa with early life stages that may be particularly vulnerable (e.g. molluscs, echinoderms) or robust (e.g. arthropods, cnidarians) to abiotic stress. We provide a list of recommendations for future multiple stressor studies, particularly those focussed on early marine life stages. This article is protected by copyright. All rights reserved.

Description: Vegetation phenology is a sensitive indicator of the dynamic response of terrestrial ecosystems to climate change. In this study, the spatiotemporal pattern of vegetation dormancy onset date (DOD) and its climate controls over temperate China were examined by analysing the satellite-derived normalized difference vegetation index and concurrent climate data from 1982 to 2010. Results show that preseason (May through October) air temperature is the primary climatic control of the DOD spatial pattern across temperate China, whereas preseason cumulative precipitation is dominantly associated with the DOD spatial pattern in relatively cold regions. Temporally, the average DOD over China's temperate ecosystems has delayed by 0.13 days per year during the past three decades. However, the delay trends are not continuous throughout the 29-year period. The DOD experienced the largest delay during the 1980s, but the delay trend slowed down or even reversed during the 1990s and 2000s. Our results also show that interannual variations in DOD are most significantly related with preseason mean temperature in most ecosystems, except for the desert ecosystem for which the variations in DOD are mainly regulated by preseason cumulative precipitation. Moreover, temperature also determines the spatial pattern of temperature sensitivity of DOD, which became significantly lower as temperature increased. On the other hand, the temperature sensitivity of DOD increases with increasing precipitation, especially in relatively dry areas (e.g. temperate grassland). This finding stresses the importance of hydrological control on the response of autumn phenology to changes in temperature, which must be accounted in current temperature-driven phenological models.

Description: Ice cores are archives of climate change and possibly large solar proton events (SPEs). Wolff et al . [2012] used a single event, a nitrate peak in the GISP2-H core, which McCracken et al . [2001a] time associated with the poorly quantified 1859 Carrington event, to discredit SPE-produced, impulsive nitrate deposition in polar ice. This is not the ideal test case. We critique the Wolff et al. analysis and demonstrate that the data they used cannot detect impulsive nitrate events because of resolution limitations. We suggest re-examination of the top of the Greenland ice sheet at key intervals over the last two millennia with attention to fine resolution and replicate sampling of multiple species. This will allow further insight into polar depositional processes on a sub-seasonal scale, including atmospheric sources, transport mechanisms to the ice sheet, post-depositional interactions, and a potential SPE association.

Description: Urban green spaces provide ecosystem services to city residents, but their management is hindered by a poor understanding of their ecology. We examined a novel ecosystem service relevant to urban public health and esthetics: the consumption of littered food waste by arthropods. Theory and data from natural systems suggest that the magnitude and resilience of this service should increase with biological diversity. We measured food removal by presenting known quantities of cookies, potato chips, and hot dogs in street medians (24 sites) and parks (21 sites) in New York City, USA. At the same sites, we assessed ground-arthropod diversity and abiotic conditions, including history of flooding during Hurricane Sandy 7 months prior to the study. Arthropod diversity was greater in parks (on average 11 hexapod families and 4.7 ant species per site), than in medians (nine hexapod families and 2.7 ant species per site). However, counter to our diversity-based prediction, arthropods in medians removed 2–3 times more food per day than did those in parks. We detected no effect of flooding (at 19 sites) on this service. Instead, greater food removal was associated with the presence of the introduced pavement ant ( Tetramorium sp. E) and with hotter, drier conditions that may have increased arthropod metabolism. When vertebrates also had access to food, more was removed, indicating that arthropods and vertebrates compete for littered food. We estimate that arthropods alone could remove 4–6.5 kg of food per year in a single street median, reducing its availability to less desirable fauna such as rats. Our results suggest that species identity and habitat may be more relevant than diversity for predicting urban ecosystem services. Even small green spaces such as street medians provide ecosystem services that may complement those of larger habitat patches across the urban landscape.

Description: Environmental variation often induces shifts in functional traits, yet we know little about whether plasticity will reduce extinction risks under climate change. As climate change proceeds, phenotypic plasticity could enable species with limited dispersal capacity to persist in situ , and migrating populations of other species to establish in new sites at higher elevations or latitudes. Alternatively, climate change could induce maladaptive plasticity, reducing fitness, and potentially stalling adaptation and migration. Here, we quantified plasticity in life history, foliar morphology, and ecophysiology in Boechera stricta (Brassicaceae), a perennial forb native to the Rocky Mountains. In this region, warming winters are reducing snowpack and warming springs are advancing the timing of snow melt. We hypothesized that traits that were historically advantageous in hot and dry, low-elevation locations will be favored at higher elevation sites due to climate change. To test this hypothesis, we quantified trait variation in natural populations across an elevational gradient. We then estimated plasticity and genetic variation in common gardens at two elevations. Finally, we tested whether climatic manipulations induce plasticity, with the prediction that plants exposed to early snow removal would resemble individuals from lower elevation populations. In natural populations, foliar morphology and ecophysiology varied with elevation in the predicted directions. In the common gardens, trait plasticity was generally concordant with phenotypic clines from the natural populations. Experimental snow removal advanced flowering phenology by 7 days, which is similar in magnitude to flowering time shifts over 2–3 decades of climate change. Therefore, snow manipulations in this system can be used to predict eco-evolutionary responses to global change. Snow removal also altered foliar morphology, but in unexpected ways. Extensive plasticity could buffer against immediate fitness declines due to changing climates.

Description: Severe geomagnetic storms have a strong impact on space communication and satellite navigation systems. Forecasting the appearance of geomagnetically induced disturbances in the ionosphere is one of the urgent goals of the space weather community. The challenge is that the processes governing the distribution of the crucial ionospheric parameters has a rather poor quantitative description and the models, built using the empirical parameterisations, have limited capabilities for operational purposes. On the other hand, data assimilation techniques are becoming more and more popular for nowcasting the state of the large-scale geophysical systems. We present an example of an ionospheric data assimilation system performance assessment during a strong geomagnetic event, which took place on 26 September 2011. The first-principle model has assimilated slant total electron content measurements from a dense network of ground stations, provided by the Norwegian Mapping Authority. The results have shown satisfactory agreement with independent data and demonstrate that the assimilation model is accurate to about 2–4 TEC units, and can be used for operational purposes in high-latitude regions. The operational system performance assessment is the subject of future work.

Description: Recent studies indicate that lianas are increasing in size and abundance relative to trees in neotropical forests. As a result, forest dynamics and carbon balance may be altered through liana-induced suppression of tree growth and increases in tree mortality. Increasing atmospheric CO 2 is hypothesized to be responsible for the increase in neotropical lianas, yet no study has directly compared the relative response of tropical lianas and trees to elevated CO 2 . We explicitly tested whether tropical lianas had a larger response to elevated CO 2 than co-occurring tropical trees, and whether seasonal drought alters the response of either growth form. In two experiments conducted in central Panama, one spanning both wet and dry seasons and one restricted to the dry season, we grew liana (n=12) and tree (n=10) species in open-top growth chambers maintained at ambient or twice-ambient CO 2 levels. Seedlings of eight individuals (four lianas, four trees) were grown in the ground in each chamber for at least three months during each season. We found that both liana and tree seedlings had a significant and positive response to elevated CO 2 (in biomass, leaf area, leaf mass per area, and photosynthesis), but that the relative response to elevated CO 2 for all variables was not significantly greater for lianas than trees regardless of the season. The lack of differences in the relative response between growth forms does not support the hypothesis that elevated CO 2 is responsible for increasing liana size and abundance across the neotropics. This article is protected by copyright. All rights reserved.

Description: [1]  The last solar minimum period was anomalously extended and low in EUV irradiance compared with previous solar minima. It can readily be expected that the thermosphere and ionosphere must be correspondingly affected by this low solar activity. While there have been unanimous reports on the thermospheric changes, being cooler and lower in its density as expected, the ionospheric responses to low solar activity in previous studies were not consistent with each other, probably due to the limited ionospheric observations used for them. In this study, we utilized the measurements of total electron content (TEC) from TOPEX and JASON-1 satellites during the periods of 1992 to 2010, which includes both the last two solar minimum periods, in order to investigate how the ionosphere responded to the extremely low solar activity during the last solar minimum compared with previous solar minimum. Although the global daily mean TECs show negligible differences between the two solar minimum periods, the global TEC maps reveal that there are significant systematic differences ranging from about -30% to +50% depending on local time, latitude and season. The systematic variations of the ionospheric responses seem to mainly result from the relative effects of reduced solar EUV production and reduced recombination rate due to thermospheric changes during the last solar minimum period.

Description: [1]  Some of the potentially most destructive effects of severe space weather storms are caused by the Geomagnetically Induced Currents. GICs can cause failures of electric transformers and result in wide-spread blackouts. GICs are induced by the time variability of the magnetic field, and are closely related to the time derivative of the local magnetic field perturbation. Predicting dB/dt is rather challenging, since the local magnetic perturbations and their time derivatives are both highly fluctuating quantities, especially during geomagnetic storms. The currently available first-principles based and empirical models cannot predict the detailed minute-scale or even faster time variation of the local magnetic field. On the other hand, Pulkkinen et al. [2013] demonstrated recently that several models can predict with positive skill scores whether the horizontal component of dB/dt at a given magnetometer station will exceed some threshold value in a 20-minute time interval. In this paper we investigate if one can improve the efficiency of the prediction further. We find that the Space Weather Modeling Framework, the best performing among the five models compared by Pulkkinen et al. [2013], shows significantly better skill scores in predicting the magnetic perturbation than predicting its time derivative, especially for large deviations. We also find that there is a strong correlation between the magnitude of dB/dt and the magnitude of the horizontal magnetic perturbation itself. Combining these two results one can devise an algorithm that gives better skill scores for predicting dB/dt exceeding various thresholds in 20-minute time intervals than the direct approach.

Description: [1]  As a weakly magnetized planet, Mars ionosphere/atmosphere interacts directly with the shocked solar wind plasma flow. Even though many numerical studies have been successful in reproducing numerous features of the interaction process, these earlier studies focused mainly on interaction under steady solar wind conditions. Recent observations suggest that plasma escape fluxes are significantly enhanced in response to solar wind dynamic pressure pulses. In this study, we focus on the response of the ionosphere to pressure enhancements in the solar wind. Through modeling of two idealized events using a magnetohydrodynamics model, we find that the upper ionosphere of Mars responds almost instantaneously to solar wind pressure enhancements, while the collision dominated lower ionosphere (below ~150 km) does not have noticeable changes in density. We also find that ionospheric perturbations in density, magnetic field and velocity can last more than an hour after the solar wind returns to the quiet conditions. The topside ionosphere forms complicated transient shapes in response, which may explain unexpected ionospheric behaviors in recent observations. We also find that ionospheric escape fluxes do not correlate directly with simultaneous solar wind dynamic pressure. Rather, their intensities also depend on the earlier solar wind conditions. It takes a few hours for the ionospheric/atmospheric system to reach a new quasi-equilibrium state.

Description: [1]  Combining THEMIS wave and particle observations and a quantitative calculation of linear wave growth rate, we demonstrate that magnetosonic (MS) waves can be locally excited by ion ring distributions in the Earth's magnetosphere when the ion ring energy is comparable to the local Alfven energy. MS waves in association with ion ring distributions were observed by THEMIS A on 24 November 2010 in the afternoon sector, both outside the plasmapause where the wave spectrum varied with f LHR and inside the plasmapause where the wave frequency band remained nearly constant. Our plasma instability analysis in three different regions shows that higher and narrow frequency band MS waves are excited locally outside the plasmapause, and lower and broad frequency band MS waves are excited in the region where the density slightly increases. However, there is no evidence for wave excitation inside the plasmapause, and wave propagation from a distant source is needed to explain their existence. The simulation of the MS wave growth rate spectra during this event agrees reasonably well with the observed wave magnetic field power spectra. We also simulated a MS wave event on 19 October 2011 in the dusk sector, and found that the ion ring distribution with an ion ring energy slightly higher than the local Alfven energy can excite the typical broad band MS waves outside the plasmapause.

Description: [1]  The second Radio Aurora Explorer (RAX-2) satellite has completed more than 30 conjunction experiments with the AMISR chain of incoherent scatter radars in Alaska, and Resolute Bay, Canada. Coherent radar echoing occurred during four of the passes: three when E region electron drifts exceeded the ion acoustic speed threshold and one during HF heating of the ionosphere by the HAARP heater. In this paper, we present the results for the first three passes associated with backscatter from natural irregularities. We analyze, in detail, the largest drift case because the plasma turbulence was the most intense and because the corresponding ground-to-space bi-static scattering geometry was the most favorable for magnetic aspect sensitivity analysis. A set of data analysis procedures including interference removal, autocorrelation analysis, and the application of a radar beam deconvolution algorithm mapped the distribution of E region backscatter with 3 km resolution in altitude and ∼ 0.1 ∘ in magnetic aspect angle. To our knowledge, these are the highest resolution altitude-resolved magnetic aspect sensitivity measurements made at UHF frequencies in the auroral region. In this paper, we show that, despite the large electron drift speed of ∼ 1500 m/s, the magnetic aspect sensitivity of sub-meter scale irregularities is much higher than previously reported. The root-mean-square of the aspect angle distribution varied monotonically between 0.5-0.1 ∘ for the altitude range 100-110 km. Findings from this single but compelling event suggest that sub-meter scale waves propagating at larger angles from the main E  ×  B flow direction (secondary waves) have parallel electric fields that are too small to contribute to E region electron heating. It is possible anomalous electron heating in the auroral electrojet can be explained by (a) the dynamics of those sub-meter scale waves propagating in the E  ×  B direction (primary waves) or (b) the dynamics of longer wavelengths.

Description: [1]  Working toward a physical understanding of how solar-wind/magnetosphere coupling works, four arguments are presented indicating that the solar-wind electric field v sw  × B sw does not control the rate of reconnection between the solar wind and the magnetosphere. Those four arguments are (1) that the derived rate of dayside reconnection is not equal to solar-wind electric field, (2) that electric-field driver functions can be improved by a simple modification that disallows their interpretation as the solar-wind electric field, (3) that the electric field in the magnetosheath is not equal to the electric field in the solar wind, and (4) that the magnetosphere can mass load and reduce the dayside reconnection rate without regard for the solar-wind electric field. The data is more consistent with a coupling function based on local control of the reconnection rate than the Axford conjecture that reconnection is controlled by boundary conditions irrespective of local parameters. Physical arguments that the solar-wind electric field controls dayside reconnection are absent; it is speculated that it is a coincidence that the electric field does so well at correlations with geomagnetic indices.

Description: [1]  This paper presents a case study from a single, six-hour observing period to illustrate the application of techniques developed for interferometric radio telescopes to the spectral analysis of observations of ionospheric fluctuations with sparse arrays. We have adapted the deconvolution methods used for making high dynamic range images of cosmic sources with radio arrays to making comparably high dynamic range maps of spectral power of wavelike ionospheric phenomena. In the example presented here, we have used observations of the total electron content (TEC) gradient derived from Very Large Array (VLA) observations of synchrotron emission from two galaxy clusters at 330 MHz as well as GPS-based TEC measurements from a sparse array of 33 receivers located within New Mexico near the VLA. We show that these techniques provide a significant improvement in signal to noise (S/N) of detected wavelike structures by correcting for both measurement inaccuracies and wavefront distortions. This is especially true for the GPS data when combining all available satellite/receiver pairs, which probe a larger physical area and likely have a wider variety of measurement errors than in the single-satellite case. In this instance, we found the peak S/N of the detected waves was improved by more than an order of magnitude. The data products generated by the deconvolution procedure also allow for a reconstruction of the fluctuations as a two-dimensional waveform/phase screen that can be used to correct for their effects.

Description: [1]  In this paper, we test whether time periods with hot proton temperature anisotropy are associated with EMIC waves, and whether the plasma conditions during the observed waves satisfy the linear theory threshold condition. We identify 865 events observed by the Composition DIstribution Function (CODIF) instrument onboard Cluster spacecraft 4 (SC4) during 1 January 2001 – 1 January 2011 that exhibit a positive temperature anisotropy ( A hp  =  T ⊥  h / T ∥  h  − 1) in the 10-40 keV protons. The events occur over an L range from 4 to 10 in all magnetic local times and at magnetic latitudes (MLAT) within ±50°. Of these Hot Proton Temperature Anisotropy (HPTA) events, only 68 events have electromagnetic ion cyclotron (EMIC) waves. In these 68 HPTA events, for those at 3.8〈 L  ≤ 5 and |MLAT| ≤ 10 ° , the EMIC waves with powers 〉1.0 nT 2 /Hz mainly appear in the region with f EMIC / f H , eq  〈 0.8. Two stop bands are present, one near the region with f EMIC / f H , eq  ≈ 0.33, the other in the region with 0.8 〈  f EMIC / f H , eq  〈 0.9. Most of the EMIC waves in the He, H, and 〉 H bands satisfy A hp /( A hp  + 1) 〉  f EMIC / f H , lo , A hp /( A hp  + 1) 〉 0.45 *  f EMIC / f H , lo , and A hp /( A hp  + 1) 〈 0.45 *  f EMIC / f H , lo .   f EMIC , f H , eq   and f H , lo are the EMIC wave frequency, the magnetic equatorial and the local proton gyrofrequencies. We also find that the EMIC waves predominantly occur with A hp  〉 0.25. By testing a threshold equation for the EMIC instability based on linear theory, we find that for EMIC waves with |MLAT| ≤ 10 ° in the He, H and 〉 H bands the percentages that satisfy the predicted conditions for wave growth by the threshold equation are 15.2%, 24.6% and 25.6%. For the EMIC waves with |MLAT| 〉 10 ° the percentages that satisfy the wave growth predicted conditions are only 2.8%, 2.6% and 0.0%. Finally, possible reasons for the low forecast accuracies of EMIC waves are suggested.

Description: [1]  The simultaneous onset of the preliminary impulse (PI) of the geomagnetic sudden commencement at high latitude and dayside dip equator is explained by means of the TM 0 mode waves propagating at the speed of light in the Earth-ionosphere waveguide (EIW) [Kikuchi et al., 1978]. A couple of issues remain to be addressed in the EIW model: (1) How is the TM 0 mode wave is excited by the field-aligned currents in the polar region? (2) How are the quasi-steady ionospheric currents are achieved by the TM 0 mode waves? (3) How simultaneous or delayed are the onset and peak of the equatorial PI with respect to the high latitude PI? To address these issues, we examine the TEM (TM 0 ) mode wave propagation in the finite-length transmission lines replacing the pair of FACs (magnetosphere-ionosphere (MI) transmission line) and the Earth-ionosphere waveguide (ionosphere-ground (IG) transmission line). The issue (1) is addressed by showing that a fraction of the TEM mode wave is transmitted from the MI to IG transmission lines through the polar ionosphere. To address the issues (2) and (3), we examine the properties of the finite-length IG transmission line with finite ionospheric conductivity. It is shown that the ionospheric currents start to grow instantaneously and continue to grow gradually with time constants of 1-10 sec depending on the ionospheric conductivity. The MIG transmission line enables us to explain the instantaneous onset and delayed peak time of the equatorial PI and quick electric field response of the low latitude ionosphere and inner magnetosphere.

Description: Potter et al., (2013) highlight the challenges and provide recommendations for progress in representing microclimate in Species Distribution Models (SDMs), which are widely used to predict distributions by establishing relationships between climatic variables and species presence. They show that the grid lengths of published SDMs are typically four orders of magnitude larger than the length of animals under study, and three orders of magnitude larger than plants. They conclude that the mismatch between the length scales of climate data and the species themselves is a major barrier for progress, and that the ideal spatial resolution for climate data in SDMs, notwithstanding practical constraints, is between 1 and 10 times the length of the organism. This article is protected by copyright. All rights reserved.

Description: [1]  Plasmoids and other reconnection-related signatures have been observed in Jupiter's magnetotail through analysis of magnetic field and energetic particle data. Previous studies have established the spatial distribution and recurrence period of tail reconnection events, and identified the location of a statistical x-line separating inward and outward flow. Here we present new analysis focusing specifically on 43 plasmoid signatures observed in magnetometer data in order to establish the average properties and internal structure of Jovian plasmoids. We present statistics on the observed plasmoid length scale, duration, radial position, and local time distribution. On average, the observed plasmoids have a ~3 R J radial extent and ~7 minute duration, and result in the closure of ~4-8 GWb of open flux from reconnection of open field lines in the post-plasmoid plasma sheet. We also determine the amount of mass released and the magnetic flux closed in order to understand the role of tail reconnection in the transport of mass and flux in Jupiter's magnetosphere. The observed plasmoid properties are consistent with a mass loss rate of ~0.7-120 kg/s and a flux closure rate of ~7-70 GWb/day. We conclude that tail reconnection and plasmoid release is an important method of flux transport at Jupiter but likely cannot account for the mass input from Io, suggesting that additional mass loss mechanisms may be significant. Finally, we examine the plasmoid interior structure through minimum variance analysis and find that most plasmoids lack a core field and are better described by magnetic loops rather than flux ropes.

Description: [1]  Hot flow anomalies (HFAs) represent a subset of solar wind discontinuities interacting with collisionless bow shocks. They are typically formed when the normal component of the motional (convective) electric field points toward the embedded current sheet on at least one of its sides. The core region of an HFA contains hot and highly deflected ion flows and rather low and turbulent magnetic field. In this paper, we report observations of possible HFA-like events at Mercury identified over a course of two planetary years. Using data from the orbital phase of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, we identify a representative ensemble of active current sheets magnetically connected to Mercury's bow shock. We show that some of these events exhibit magnetic and particle signatures of HFAs similar to those observed at other planets, and present their key physical characteristics. Our analysis suggests that Mercury's bow shock does not only mediate the flow of supersonic solar wind plasma but also provides conditions for local particle acceleration and heating as predicted by previous numerical simulations. Together with earlier observations of HFA activity at Earth, Venus, Mars, and Saturn, our results suggest that hot flow anomalies could be a common property of planetary bow shocks, and show that the characteristic size of these events is controlled by the bow shock standoff distance and/or local solar wind conditions.

Description: [1]  This paper investigates the influence of two solar eclipses on the ionosphere complexity measures: Tsallis entropy, Renyi entropy, Hurst exponent, beta exponent, fractal dimension. The study used GPS TEC measured at 3 locations in Japan during the solar eclipses of 22 July 2009 and 21 May 2012.This is the first effort to compare the complexity measures by comparing TEC time series of the eclipse day with those from the day before and day after the eclipse. It was found from analysis of the TEC observations that there were no abnormal variations of the complexity parameters from their expected values for either eclipse. Model calculations also show that TEC deviations during the eclipses are small.

Description: [1]  We have analyzed the data of the world neutron monitor network for the first ground level enhancement of solar cycle 24, the GLE on May 17, 2012. A newly computed neutron monitor yield function and an inverse method are applied to estimate the energy spectrum, anisotropy axis direction and pitch-angle distribution of the high-energy solar particles in interplanetary space. The method includes the determination of the asymptotic viewing cones of neutron monitor stations through computations of trajectories of cosmic rays in a model magnetosphere. The cosmic ray particle trajectories are determined with the MAGNETOCOSMICS code using Tsyganenko 1989 and IGRF models. Subsequent calculation of the neutron monitor responses with the model function is carried out, that represents an initial guess of the inverse problem. Derivation of the solar energetic particle characteristics is fulfilled by fitting the data of the global neutron monitor network using the Levenberg-Marquardt method over the nine-dimensional parameter space. The pitch-angle distribution and rigidity spectrum of high-energy protons are obtained as function of time in the course of the GLE. The angular distribution appears quite complicated. It comprises a focused beam along the interplanetary magnetic field line from the Sun and a loss-cone feature around the opposite direction, possibly indicative of the particle transport in interplanetary magnetic field structures associated with previous coronal mass ejections.

Description: [1]  Geomagnetic activity is strongly controlled by solar wind and Interplanetary Magnetic Field (IMF) conditions, especially the southward component of IMF (IMF Bs). We analyze the statistical properties of IMF Bs at 1 AU using in situ observations for more than a solar cycle (1995 - 2010). IMF Bs-events are defined as continuous IMF Bs intervals with varying thresholds of Bs magnitude and duration, and categorized by different solar wind structures, such as magnetic cloud (MC), interplanetary small-scale magnetic flux rope (ISMFR), interplanetary coronal mass ejection (ICME) without MC signature (ejecta), stream interacting region (SIR), and shock, as well as events unrelated with well-defined solar wind structures. The statistical properties of IMF Bs-events and their geoeffectiveness are investigated in detail based on satellite and ground measurements. We find that the integrated duration and number of Bs-events follow the sunspot number when Bz 〈 -5 nT. We also find that in extreme Bs-events (t 〉 6 hours, Bz 〈 -10 nT), a majority (53 %) are related to MC and 10 % are related with ejecta, but nearly a quarter are not associated with any well-defined solar wind structure. We find different geomagnetic responsesfor Bs-events with comparable duration and magnitude depending on what type of solar wind structures they are associated with. We also find that great Bs-events (t 〉 3 hours, Bz 〈 -10 nT) do not always trigger magnetic storms.

Description: [1]  This technique paper describes a novel method for quantitatively and routinely identifying auroral breakup following substorm onset using the Time History of Events and Macroscale Interactions During Substorms (THEMIS) all-sky imagers (ASIs). Substorm onset is characterised by a brightening of the aurora that is followed by auroral poleward expansion and auroral breakup. This breakup can be identified by a sharp increase in the auroral intensity i(t) and the time derivative of auroral intensity i'(t) . Utilising both i(t) and i'(t) we have developed an algorithm for identifying the time interval and spatial location of auroral breakup during the substorm expansion phase within the field of view of ASI data based solely on quantifiable characteristics of the optical auroral emissions. We compare the time interval determined by the algorithm to independently identified auroral onset times from three previously published studies. In each case the time interval determined by the algorithm is within error of the onset independently identified by the prior studies. We further show the utility of the algorithm by comparing the breakup intervals determined using the automated algorithm to an independent list of substorm onset times. We demonstrate that up to 50% of the breakup intervals characterised by the algorithm are within the uncertainty of the times identified in the independent list. The quantitative description and routine identification of an interval of auroral brightening during the substorm expansion phase provides a foundation for unbiased statistical analysis of the aurora to probe the physics of the auroral substorm as a new scientific tool for aiding the identification of the processes leading to auroral substorm onset.

Description: [1]  We applied the Grad-Shafranov (GS) reconstruction technique to Martian magnetic flux ropes observed by Mars Global Surveyor in order to estimate their spatial structures. This technique can provide a magnetic field map of their cross section from single spacecraft data, under the assumption that the structure is two-dimensional, magneto-hydrostatic, and time-independent. We succeeded in recovering the spatial structure for 70 events observed between April 1999 and November 2006. The reconstruction results indicate that the flux rope axes were mostly oriented horizontal to the Martian surface, and were randomly distributed with respect to the typical plasma streamline. A subset of events with duration longer than 240 sec was observed at solar zenith angles larger than 75 deg. These events all occur downstream from strong crustal magnetic field in the southern hemisphere, indicating an association between the crustal fields and the detected flux ropes. Using the shape and size of the flux ropes obtained from the GS reconstruction, we estimate lower limits on their volume that span 2–3 orders of magnitude, with larger flux ropes observed downstream from strong crustal magnetic fields. Estimated ion escape rates associated with flux ropes are of the order of 10 22 –10 23 ion/sec, being approximately 10% of previously estimated escape rates during solar minimum.

Description: Climate-driven range shifts are ongoing in pelagic marine environments, and ecosystems must respond to combined effects of altered species distributions and environmental drivers. Hypoxic oxygen minimum zones (OMZs) in midwater environments are shoaling globally; this can affect distributions of species both geographically and vertically along with predator–prey dynamics. Humboldt (jumbo) squid ( Dosidicus gigas ) are highly migratory predators adapted to hypoxic conditions that may be deleterious to their competitors and predators. Consequently, OMZ shoaling may preferentially facilitate foraging opportunities for Humboldt squid. With two separate modeling approaches using unique, long-term data based on in situ observations of predator, prey, and environmental variables, our analyses suggest that Humboldt squid are indirectly affected by OMZ shoaling through effects on a primary food source, myctophid fishes. Our results suggest that this indirect linkage between hypoxia and foraging is an important driver of the ongoing range expansion of Humboldt squid in the northeastern Pacific Ocean.

Description: Transmission of avian malaria in the Hawaiian Islands varies across altitudinal gradients and is greatest at elevations below 1,500 m where both temperature and moisture are favorable for the sole mosquito vector, Culex quinquefasciatus , and extrinsic sporogonic development of the parasite, Plasmodium relictum . Potential consequences of global warming on this system have been recognized for over a decade with concerns that increases in mean temperatures could lead to expansion of malaria into habitats where cool temperatures currently limit transmission to highly susceptible endemic forest birds. Recent declines in two endangered species on the island of Kaua'i, the ‘Akikiki ( Oreomystis bairdi ) and ‘Akeke'e ( Loxops caeruleirostris ), and retreat of more common native honeycreepers to the last remaining high elevation habitat on the Alaka'i Plateau suggest that predicted changes in disease transmission may be occurring. We compared prevalence of malarial infections in forest birds that were sampled at three locations on the Plateau between 1994-1997 and again between 2007-2013, and also evaluated changes in the occurrence of mosquito larvae in available aquatic habitats during the same time periods. Prevalence of infection increased significantly at the lower (1,100 m, 10.3% to 28.2%), middle (1,250 m, 8.4% to 12.2%) and upper ends of the Plateau (1,350 m, 2.0% to 19.3%). A concurrent increase in detections of Culex larvae in aquatic habitats associated with stream margins indicates that populations of the vector are also increasing. These increases are at least in part due to local transmission because overall prevalence in Kaua'i ‘Elepaio ( Chasiempis sclateri ), a sedentary native species, has increased from 17.2% to 27.0%. Increasing mean air temperatures, declining precipitation, and changes in streamflow that have taken place over the past 20 years are creating environmental conditions throughout major portions of the Alaka'i Plateau that support increased transmission of avian malaria. This article is protected by copyright. All rights reserved.

Description: [1]  From a survey of Polar plasma waves conducted over the interval 1 April, 1996 to 4 April, 1997 (during solar minimum) at and inside the plasmasphere, magnetosonic waves were detected at all local times with a slight preference of occurrence in the midnight-postmidnight sector at L = 3 to 4. The waves occurred primarily during heightened geomagnetic (AE) activity. Wave occurrence (and intensities) peaked at ~ ±5° of the magnetic equator, with half-maxima at ~ ±10°. For other wave events, magnetosonic waves were also detected as far from the equator as +20° and -60° MLAT, but at lower intensities. An extreme magnetosonic wave intensity event of amplitude B w  = ~ ± 1 nT and E w  = ~ ± 25 mV/m was detected during the survey period. The event occurred near local midnight (0022 MLT), at the magnetic equator (MLAT = -0.5°), at the plasmapause (L = 3.5), and during an intense substorm/convection event (AE = 624 nT; SYM-H = -33 nT). If more stringent requirements (| MLAT| ≤ 5° and AE 〉 300 nT) are imposed, the wave occurrence rate approaches ~50% for the 23 to 00 MLT bin at L = 3 to 4. This strong local time anisotropy in the location of magnetosonic wave occurrence rate supports the idea of generation by protons injected from the plasmasheet into the midnight sector magnetosphere by substorm electric fields. Magnetosonic waves were also detected near late morning (1031 MLT) during relative geomagnetic quiet (low AE). We mention that one possible generation mechanism is a recovering/expanding plasmasphere engulfing preexisting energetic ions, which in turn leads to an ion instability. The wave magnetic component oscillations are aligned along B 0 , the ambient magnetic field direction, and the electric component oscillations are orthogonal to B 0 , indicating linear polarization. The magnetosonic wave amplitudes decreased at locations further from the magnetic equator, while transverse whistler mode wave amplitudes increased. We argue that intense magnetosonic waves are always present somewhere in the magnetosphere during strong substorm/convection events. We thus suggest that modelers use dynamic particle tracing codes and the maximum (rather than average) wave amplitudes to simulate wave-particle interactions.

Description: Biomass carbon accumulation in forest ecosystems is a widespread phenomenon at both regional and global scales. However, as coupled carbon-climate models predicted, a positive feedback could be triggered if accelerated soil carbon decomposition offsets enhanced vegetation growth under a warming climate. It is thus crucial to reveal whether and how soil carbon stock in forest ecosystems has changed over recent decades. However, large-scale changes in soil carbon stock across forest ecosystems have not yet been carefully examined at both regional and global scales, which have been widely perceived as a big bottleneck in untangling carbon-climate feedback. Using newly-developed database and sophisticated data-mining approach, here we evaluated temporal changes in topsoil carbon stock across major forest ecosystem in China and analyzed potential drivers in soil carbon dynamics over broad geographic scale. Our results indicated that topsoil carbon stock increased significantly within all of five major forest types during the period of 1980s-2000s, with an overall rate of 20.0 g C m −2 yr −1 (95% confidence interval, 14.1-25.5). The magnitude of soil carbon accumulation across coniferous forests and coniferous/broadleaved mixed forests exhibited meaningful increases with both mean annual temperature and precipitation. Moreover, soil carbon dynamics across these forest ecosystems was positively associated with clay content, with a larger amount of SOC accumulation occurring in fine-textured soils. In contrast, changes in soil carbon stock across broadleaved forests were insensitive to either climatic or edaphic variables. Overall, these results suggest that soil carbon accumulation does not counteract vegetation carbon sequestration across China's forest ecosystems. The combination of soil carbon accumulation and vegetation carbon sequestration triggers a negative feedback to climate warming, rather than a positive feedback predicted by coupled carbon-climate models. This article is protected by copyright. All rights reserved.

Description: Predicted decreases in water availability across the temperate forest biome have the potential to offset gains in carbon (C) uptake from phenology trends, rising atmospheric CO 2 , and nitrogen deposition. While it is well-established that severe droughts reduce the C sink of forests by inducing tree mortality, the impacts of mild but chronic water stress on forest phenology and physiology are largely unknown. We quantified the C consequences of chronic water stress using a 13-year record of tree growth (n = 200 trees), soil moisture, and ecosystem C balance at the Morgan-Monroe State Forest (MMSF) in Indiana, and a regional 11-year record of tree growth (n 〉300,000 trees) and water availability for the 20 most dominant deciduous broadleaf tree species across the Eastern and Midwestern USA. We show that despite ~26 more days of C assimilation by trees at the MMSF, increasing water stress decreased the number of days of wood production by ~42 days over the same period, reducing the annual accrual of C in woody biomass by 41%. Across the deciduous forest region, water stress induced similar declines in tree growth, particularly for water-demanding “mesophytic” tree species. Given the current replacement of water-stress adapted “xerophytic” tree species by mesophytic tree species, we estimate that chronic water stress has the potential to decrease the C sink of deciduous forests by up to 17% (0.04 Pg C yr −1 ) in the coming decades. This reduction in the C sink due to mesophication and chronic water stress is equivalent to an additional 1 to 3 days of global C emissions from fossil fuel burning each year. Collectively, our results indicate that regional declines in water availability may offset the growth-enhancing effects of other global changes and reduce the extent to which forests ameliorate climate warming. This article is protected by copyright. All rights reserved.

Description: [1]  On January 9, 2002 and November 14, 2001, the São Luís 30 MHz coherent backscatter radar observed unusual day-time echoes scattered from the equatorial electrojet. The electrojet echoing layers on these days, as seen in the range time intensity (RTI) maps, exhibited quasi-periodic oscillations. Time-frequency decomposition of the magnetic field perturbations ΔH , measured simultaneously by the ground-based magnetometers, also showed evidence of short period waves. The ground-based observations were aided by measurements of the brightness temperature in the water vapor and infrared bands made by the GOES 8 satellite. The GOES 8 satellite measurements indicated evidence of deep tropospheric convection activities, which are favorable for the launch of atmospheric gravity waves (AGW) near São Luís. Our multi-technique investigation, combined with an analysis of the equatorial electric field and current density, indicates that AGW forcing could have been responsible, via coupling with E-region electric fields, for the short-period electrojet oscillations observed over São Luís.

Description: [1]  The diurnal variation of the global electric circuit is investigated using the World Wide Lightning Location Network (WWLLN), which has been shown to identify nearly all thunderstorms ( [16], using WWLLN data from 2005). To create an estimate of global electric circuit activity, a clustering algorithm is applied to the WWLLN dataset to identify global thunderstorms from 2010 – 2013. Annual, seasonal, and regional thunderstorm activity is investigated in this new WWLLN thunderstorm dataset in order to estimate the source behavior of the global electric circuit. Through the clustering algorithm, the total number of active thunderstorms are counted every 30 minutes creating a measure of the global electric circuit source function. The thunderstorm clusters are compared to precipitation radar data from the Tropical Rainfall Measurement Mission satellite and with case studies of thunderstorm evolution. [2]  The clustering algorithm reveals an average of 660 ± 70 thunderstorms active at any given time with a peak-to-peak variation of 36%. The highest number of thunderstorms occurs in November (720 ± 90) and the lowest number occurs in January (610 ± 80). Thunderstorm cluster and electrified storm cloud activity are combined with thunderstorm overflight current measurements to estimate the global electric circuit thunderstorm contribution current to be 1090 ± 70 A with a variation of 24%. By utilizing the global coverage and high time resolution of WWLLN, the total active thunderstorm count and current is shown to be less than previous estimates based on compiled climatologies.

Description: [1]  Dynamics of the dayside magnetosphere and proton radiation belt was analyzed during unusual magnetic storm on 21 January 2005. We have found that during the storm from 1712 to 2400 UT, the subsolar magnetopause was continuously located inside geosynchronous orbit due to strong compression. The compression was found to be extremely strong from 1846 to 2035 UT when the dense plasma of fast erupting filament produced the solar wind dynamic pressure Pd peaked up to 〉100 nPa and, in the first time, the upstream solar wind was observed at geosynchronous orbit during almost 2 hours. Under the extreme compression, the outer magnetosphere at L  〉 5 was pushed inward and the outer radiation belt particles with energies of several tens of keV moved earthward, became adiabatically accelerated and accumulated in the inner magnetosphere at L  〈 4 that produced the intensified ring current with an exceptionally long lifetime. The observations were compared with predictions of various empirical and first principles models. All the models failed to predict the magnetospheric dynamics under the extreme compression when the minimal magnetopause distance was estimated to be ~3 Re. The inconsistencies between the model predictions and observations might result from distortions of plasma measurements by extreme heliospheric conditions consisting in very fast solar wind streams (~1000 km/s) and intense fluxes of solar energetic particles. We speculated that anomalous dynamics of the magnetosphere could be well described by the models if the He abundance in the solar wind was assumed to be 〉20%, which is well appropriate for erupting filaments and which is in agreement with the upper 27% threshold for the He/H ratio obtained from Cluster measurements.

Description: [1]  Type III radio bursts are produced near the local electron plasma frequency and/or near its harmonic by fast electrons ejected from the solar active regions and moving through the corona and solar wind. These bursts have dynamic spectra with frequency rapidly falling with time. This paper presents two new methods developed to detect type III bursts automatically in the data from High Frequency Receiver (HFR) of the STEREO/WAVES (S/WAVES) radio instrument onboard the STEREO spacecraft. The first technique is applicable to the low frequency band (HFR-1: 125 kHz to 1.975 MHz) only. This technique can possibly be implemented in on-board satellite software aimed at preliminary detection of bursts and identification of time intervals with relatively high solar activity. In the second technique the bursts are detected in both the low frequency band and the high frequency band (HFR-2: 2.025 MHz to 16.025 MHz), with the computational burden being higher by one order of magnitude as compared with that for the first technique. Preliminary tests of the method show that the performance of the first technique is quite high, P dL  = 72 % ± 3 %. The performance of the second technique is considerably higher, P dL  +  H  = 81 % ± 1%, while the number of false alarms does not exceed 10% for one daily spectrum.

Description: [1]  A dipolarizing flux bundle (DFB) is a small magnetotail flux tube (typically 〈 ~3 R E in X GSM and Y GSM ) with a significantly more dipolar magnetic field than its background. Dipolarizing flux bundles typically propagate earthward at a high speed from the near-Earth reconnection region. Knowledge of a DFB's flux transport properties leads to better understanding of near-Earth (X = -6 to -30 R E ) magnetotail flux transport and thus conversion of magnetic energy to kinetic and thermal plasma energy following magnetic reconnection. We explore DFB properties with a statistical study using data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission. To establish the importance of DFB flux transport, we compare it with transport by bursty bulk flows (BBFs) that typically envelop DFBs. Because DFBs coexist with flow bursts inside BBFs, they contribute 〉65% of BBF flux transport, even though they last only ~30% as long as BBFs. The rate of DFB flux transport increases with proximity to Earth and to the pre-midnight sector, as well as with geomagnetic activity and distance from the neutral sheet. Under the latter two conditions the total flux transport by a typical DFB also increases. Dipolarizing flux bundles appear more often during increased geomagnetic activity. Since BBFs have been previously shown to be the major flux transporters in the tail, we conclude that DFBs are the dominant drivers of this transport. The occurrence rate of DFBs as a function of location and geomagnetic activity informs us about processes that shape global convection and energy conversion

Description: [1]  The substorm current wedge (SCW) is a fundamental component of geomagnetic substorms. Models tend to describe the SCW as a simple line current flowing into the ionosphere towards dawn and out of the ionosphere towards dusk, linked by a westward electrojet. We use multi-spacecraft observations from perigee passes of the Cluster 1 and 4 spacecraft during a substorm on 15 Jan 2010, in conjunction with ground-based observations, to examine the spatial structuring and temporal variability of the SCW. At this time, the spacecraft travelled east-west azimuthally above the auroral region. We show that the SCW has significant azimuthal sub-structure on scales of 100 km at altitudes of 4,000-7,000 km. We identify 26 individual current sheets in the Cluster 4 data and 34 individual current sheets in the Cluster 1 data, with Cluster 1 passing through the SCW 120-240 s after Cluster 4 at 1,300-2,000 km higher altitude. Both spacecraft observed large-scale regions of net upward and downward field-aligned current, consistent with the large-scale characteristics of the SCW, although sheets of oppositely directed currents were observed within both regions. We show that the majority of these current sheets were closely aligned to a north-south direction,in contrast to the expected east-west orientation of the pre-onset aurora. Comparing our results with observations of the field-aligned current associated with bursty bulk flows (BBFs) we conclude that significant questions remain for the explanation of SCW structuring by BBF driven “wedgelets”. Our results therefore represent constraints on future modelling and theoretical frameworks on the generation of the SCW.

Description: [1]  Large horizontal winds and wind shears have been measured in the lower thermosphere by rockets, lidars, and non-specular meteor radars. This paper describes a detailed analysis of 3 multi-hour non-specular meteor radar data sets collected at the Jicamarca Radio Observatory. This provides some of the highest resolution sustained measurements in this part of the atmosphere. These show: (1) intense wind speeds, maintaining 180 m/s for half an hour and 160 m/s for another half an hour; (2) winds structured in layers that move up or, more commonly, down in the pre-dawn hours at rates of a few km/hr; (3) intense wind shears that typically persist at around 50 m/s/km but, in one instance, sustains values approaching 100 m/s/km for a few hours.

Description: [1]  We present results from an analysis of high-latitude ionosphere-thermosphere (IT) coupling to the solar wind during a moderate magnetic storm which occurred on 5-6 August 2011. During the storm, a multi-point set of observations of the ionosphere and thermosphere was available. We make use of ionospheric measurements of electromagnetic and particle energy made by the Defense Meteorological Satellite Program (DMSP), and neutral densities measured by the Gravity Recovery and Climate Experiment (GRACE) satellite to infer: (1) the energy budget and (2) timing of the energy transfer process during the storm. We conclude that the primary location for energy input to the IT system may be the extremely high latitude region. We suggest that the total energy available to the IT system is not completely captured either by observation or empirical models.

Description: [1]  The level of solar activity varies from cycle to cycle. This variability is probably caused by a combination of nonlinear and random effects. Based on surface flux transport simulations, we show that the observed inflows into active regions and towards the activity belts provide an important nonlinearity in the framework of Babcock-Leighton model for the solar dynamo. Inclusion of these inflows also leads to a reproduction of the observed proportionality between the open heliospheric flux during activity minima and the maximum sunspot number of the following cycle. A substantial component of the random variability of the cycle strength is associated with the cross-equatorial flux plumes that occur when large, highly-tilted sunspot groups emerge close to the equator. We show that the flux transported by these events is important for the amplitude of the polar fields and open flux during activity minima. The combined action of inflows and cross-equatorial flux plumes provides an explanation for the weakness of the polar fields at the end of solar cycle 23 (and hence for the relative weakness of solar cycle 24).

Description: [1]  We present the first direct measurement of neutral oxygen in the lunar exosphere, detected by the Chandrayaan-1 Energetic Neutral Analyzer (CENA). With the lunar surface consisting of about 60% of oxygen in number, the neutral oxygen detected in CENA's energy range (11 eV – 3.3 keV) is attributed to have originated from the lunar surface, where it is released through solar wind ion sputtering. We verify this proposition by comparing the measured oxygen content in two different mass spectra groups with ion sputtering theory. One group contains mass spectra that were recorded when the solar wind consisted of almost pure hydrogen and the other group contains mass spectra that were recorded when the helium content in the solar wind was very high (〉3.5%). Since helium is a much more effective sputtering agent than hydrogen (5% of alpha particles present in the solar wind typically contribute 30% of the total sputter yield), these two groups should show clear differences in the oxygen sputter yield. Fitting of CENA's mass spectra with calibration spectra from ground and in-flight data resulted in the detection of a robust oxygen signal, with a flux of 0.2 to 0.4 times the flux of backscattered hydrogen, depending, as expected, on the solar wind helium content and particle velocity. These measurements present the first in-situ detection of oxygen in the lunar exosphere. For the two solar wind types observed, we derive sub-solar surface oxygen atom densities of N 0  = (1.1 ± 0.3) ⋅ 10 7 m − 3 and (1.4 ± 0.4) ⋅ 10 7 m − 3 , respectively, which agree well with earlier model predictions and measured upper limits. From these surface densities we derive, by modeling, column densities of N C  = (1.5 ± 0.5) ⋅ 10 13 m − 2 and (1.6 ± 0.5) ⋅ 10 13 m − 2 . [2]  In addition, in the CENA mass spectra, we identified for the first time a helium component. This helium is attributed to backscattering of solar wind helium (alpha particles) from the lunar surface as neutral energetic helium atoms, which has been observed for the first time. This identification is supported by the characteristic energy of the measured helium atoms, which is roughly four times the energy of reflected solar wind hydrogen, and the correlation with solar wind helium content.

Description: [1]  The diffuse aurora is an almost permanent feature in the Earth's upper polar atmosphere, providing the major source of ionizing energy input into the high-latitude region. Previous theoretical and observational studies have demonstrated that whistler-mode chorus scattering primarily accounts for intense nightside diffuse auroral precipitation within ~ 8 R E , but what causes the dayside diffuse aurora remains poorly understood. Using conjugate satellite wave and particle observations on 13 August 2009 from the THEMIS spacecraft and ground-based all-sky imager measurements at the South Pole on the dayside, we perform a quantitative analysis of wave driven diffusion and electron precipitation. Our results demonstrate that the dayside chorus scattering was the dominant contributor to the observed dayside diffuse auroral precipitation and that the chorus wave intensity primarily controlled its brightness, indicating that dayside chorus can be the major driver of the Earth's dayside diffuse aurora. While further investigations are required to bring closure to the origin of the dayside diffuse aurora under differing solar wind conditions and geomagnetic situations, our finding is an important complement to recent work on the formation mechanism of the diffuse aurora and provides improved understanding of the roles of resonant wave-particle interactions in diffuse auroral precipitation pattern on a global scale.

Description: [1]  Ultra Low Frequency (ULF: 0.001-5 Hz) magnetic records have recently been used in the search for short term earthquake prediction methods. The separation of local and global effects in the magnetic records is the greatest challenge in this research area. Geomagnetic indices are often used to predict global ULF magnetic behavior where it is assumed that increases in a geomagnetic index correspond with an increase in ULF power. This paper examines the relationships between geomagnetic indices and ULF power, spectral polarization ratio and the relationship between the spectral polarization ratio and solar wind parameters. The power in the ULF, Pc3-5 bands (10-600 s) shows a linear correlation coefficient of  0.2 with the Kp magnetic activity index. The correlation varies with magnetic local time (MLT) and latitude. The correlation coefficient is inversely related to the integrated power in the ULF Pc3 band (10-45 s) over MLT and magnetic latitude. The ratio of spectral powers Z ( ω )/ G ( ω ) is discussed and shown to be a promising parameter in the search for earthquake precursor signals in ULF records.

Description: [1]  Recent testing of a quantitative model describing the classical (region-1-sense, referred to as the R1 current loop) substorm current wedge (SCW) revealed systematic discrepancies between the observed and predicted amplitudes, which suggested us to include additional region-2-sense currents (R2-loop) earthward of the dipolarized region (SCW2L model). In this paper we discuss alternative circuit geometries of the 3d substorm current system and interpret simultaneous observations of the magnetic field dipolarizations by NOAA Geostationary Operational Environmental Satellite (GOES) and by NASA Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft, to quantitatively investigate the SCW2L model parameters. During two cases of a dipole-like magnetotail configuration, the dipolarization/injection front fortuitously stopped at r  ∼ 9 Re for the entire duration of ∼ 30 min-long SCW-related dipolarization within a unique, radially-distributed multi-spacecraft constellation, which allowed us to determine the locations and total currents of both SCW2L loops. In addition, we conducted a survey of the dipolarization amplitudes in events, simultaneously observed at 6.6 Re (GOES) and 11 Re (THEMIS) under a wide range of magnetotail conditions. We infer that the ratio I 2 / I 1 varies in the range 0.2 to 0.6 (median value 0.4) and that the equatorial part of the R2 current loop stays at the distance r  〉 6.6 Re in the case of a dipole-like field geometry ( BZ 0  〉 75 nT at 6.6 Re prior to the onset), but it is located at r  〈 6.6 Re in the case of a stretched magnetic field configuration (with BZ 0  〈 60 nT). Since the ground midlatitude perturbations are sensitive to the combined effect of the R1- and R2-sense current loops with the total current roughly equal to I 1  −  I 2 , the ratio I 2 / I 1 becomes an important issue when attempting to monitor the current disruption intensity from ground observations.

Description: Model predictions of extinction risks from anthropogenic climate change are dire, but still overly simplistic. To reliably predict at-risk species we need to know which species are currently responding, which are not, and what traits are mediating the responses. For mammals, we have yet to identify overarching physiological, behavioral, or biogeographic traits determining species' responses to climate change, but they must exist. To date, 73 mammal species in North America and eight additional species worldwide have been assessed for responses to climate change, including local extirpations, range contractions and shifts, decreased abundance, phenological shifts, morphological or genetic changes. Only 52% of those species have responded as expected, 7% responded opposite to expectations, and the remaining 41% have not responded. Which mammals are and are not responding to climate change is mediated predominantly by body size and activity times (phylogenetic multivariate logistic regressions, P  〈 0.0001). Large mammals respond more, for example, an elk is 27 times more likely to respond to climate change than a shrew. Obligate diurnal and nocturnal mammals are more than twice as likely to respond as mammals with flexible activity times ( P  〈 0.0001). Among the other traits examined, species with higher latitudinal and elevational ranges were more likely to respond to climate change in some analyses, whereas hibernation, heterothermy, burrowing, nesting, and study location did not influence responses. These results indicate that some mammal species can behaviorally escape climate change whereas others cannot, analogous to paleontology's climate sheltering hypothesis. Including body size and activity flexibility traits into future extinction risk forecasts should substantially improve their predictive utility for conservation and management.

Description: Controls on the fate of ~ 277 Pg of soil organic carbon (C) stored in permafrost peatland soils remain poorly understood despite the potential for a significant positive feedback to climate change. Our objective was to quantify the temperature, moisture, organic matter, and microbial controls on soil organic carbon (SOC) losses following permafrost thaw in peat soils across Alaska. We compared the carbon dioxide (CO 2 ) and methane (CH 4 ) emissions from peat samples collected at active layer and permafrost depths when incubated aerobically and anaerobically at -5, -0.5, +4 and +20°C. Temperature had a strong, positive effect on C emissions; global warming potential (GWP) was 〉 3x larger at 20°C than at 4°C. Anaerobic conditions significantly reduced CO 2 emissions and GWP by 47% at 20°C but did not have a significant effect at -0.5°C. Net anaerobic CH 4 production over 30 days was 7.1 ± 2.8 μ g CH 4 -C gC −1 at 20°C. Cumulative CO 2 emissions were related to organic matter chemistry and best predicted by the relative abundance of polysaccharides and proteins (R 2 =0.81) in SOC. Carbon emissions (CO 2 -C + CH 4 -C) from the active layer depth peat ranged from 77% larger to not significantly different than permafrost depths and varied depending on the peat type and peat decomposition stage rather than thermal state. Potential SOC losses with warming depend not only on the magnitude of temperature increase and hydrology but also organic matter quality, permafrost history, and vegetation dynamics, which will ultimately determine net radiative forcing due to permafrost thaw. This article is protected by copyright. All rights reserved.

Description: Thermal stress affects organism performance differently depending on the ambient temperature to which they are acclimatized, which varies along latitudinal gradients. This study investigated whether differences in physiological responses to temperature are consistent with regional differences in temperature regimes for the stony coral Oculina patagonica . To resolve this question we experimentally assessed how colonies originating from four different locations characterized by 〉3°C variation in mean maximum annual temperature responded to warming from 20 to 32°C. We assessed plasticity in symbiont identity, density, and photosynthetic properties, together with changes in host tissue biomass. Results show that, without changes in the type of symbiont hosted by coral colonies, O. patagonica has limited capacity to acclimatize to future warming. We found little evidence of variation in overall thermal tolerance, or in thermal optima, in response to spatial variation in ambient temperature. Given that the invader O. patagonica is a relatively new member of the Mediterranean coral fauna our results also suggest that coral populations may need to remain isolated for a long period of time for thermal adaptation to potentially take place. Our study indicates that for O. patagonica , mortality associated with thermal stress manifests primarily through tissue breakdown under moderate but prolonged warming (which does not impair symbiont photosynthesis and, therefore, does not lead to bleaching). Consequently, projected global warming is likely to causes repeat incidents of partial and whole colony mortality and might drive a gradual range contraction of Mediterranean corals. This article is protected by copyright. All rights reserved.

Description: We present Cluster observations of wave-particle interactions during an earthward-propagating dipolarization front (DF) and associated fast plasma bulk flows detected at the central current sheet in Earth's magnetotail. During this period, flux tubes behind the DF frequently contain more energetic or hotter ions than did the pre-existing flux tubes ahead of the DF. On the other hand, electrons within the DF flux tubes heat less, or are even colder, than were the pre-existing populations, and are often accompanied by superposed isolated beams. At the same time, electrostatic emissions are strongly enhanced over a wide range of frequencies (up to several times the electron cyclotron frequency) behind the DFs. This low-frequency electrostatic wave power is well correlated with ion energization. From linear theory, we find two wave modes: a high-frequency beam mode and a low-frequency whistler mode that are associated with the electron beam component. We attribute the generation of whistlers to electron beams that persist for a while before undergoing rapid thermalization. The existence of isolated beam components behind DFs detected during the 4-sec Cluster spin period indicates that DFs either provide a continuous source of electron beams or facilitate a physical process that maintains the beams against rapid thermalization. Our analysis suggests that the earthward motion of the DF flux tube, via Fermi acceleration as the magnetic field lines behind the DF shorten, can lead to the persistent electron beams that generate whistler mode waves, which in turn can heat ions. This scenario, by which free energy in electron beams generates waves that then heat ions, accounts for the Cluster observations of different energization behaviors between electrons and ions behind DFs.

Description: We examine a unique data set from seven Hubble Space Telescope (HST) ‘visits’ that imaged Saturn's northern dayside ultraviolet emissions exhibiting usual circumpolar ‘auroral oval’ morphologies, during which Cassini measured the interplanetary magnetic field (IMF) upstream of Saturn's bow shock over intervals of several hours. The auroras generally consist of a dawn arc extending towards noon centered near ~15º co-latitude, together with intermittent patchy forms at ~10º co-latitude and poleward thereof, located between noon and dusk. The dawn arc is a persistent feature, but exhibits variations in position, width, and intensity, which have no clear relationship with the concurrent IMF. However, the patchy post-noon auroras are found to relate to the (suitably lagged and averaged) IMF B z , being present during all four visits with positive B z and absent during all three visits with negative B z . The most continuous such forms occur in the case of strongest positive B z . These results suggest that the post-noon forms are associated with reconnection and open flux production at Saturn's magnetopause, related to the similarly-interpreted bifurcated auroral arc structures previously observed in this LT sector in Cassini UVIS data, whose details remain unresolved in these HST images. One of the intervals with negative IMF B z , however, exhibits a pre-noon patch of very high latitude emission extending poleward of the dawn arc to the magnetic/spin pole, suggestive of the occurrence of lobe reconnection. Overall, these data provide evidence of significant IMF-dependence in the morphology of Saturn's dayside auroras.

Description: A three-dimensional (3D) particle-in-cell (PIC) simulation of the whistler anisotropy instability is carried out for a collisionless, homogeneous, magnetized plasma with β e  = 0.10. This is the first 3D PIC simulation of the evolution of enchanced fluctuations from this growing mode driven by an anisotropic electron velocity distribution with T ⊥  e / T ‖ e  〉 1 where ⊥ and ∥ represent directions perpendicular and parallel to the background magnetic field B o , respectively. The early-time magnetic fluctuation spectrum grows with properties reflecting the predictions of linear theory with narrowband maxima at kc / ω e  ≃ 1 and k  ×  B o  = 0, and a wavevector anisotropy in the sense of k ⊥  〈 〈  k ∥ . Here ω e represents the electron plasma frequency. At later times the fluctuations undergo both a forward transfer to shorter wavelengths, also with k ⊥  〈 〈  k ∥ , and an inverse transfer to longer wavelengths with wavevector anisotropy k ⊥  〉 〉  k ∥ . The inverse transfer is consistent with a prediction of nonlinear three-wave coupling theory.

Description: Auroral ionospheric F-region density depletions observed by PFISR (Poker Flat Incoherent Scatter Radar) during the MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) sounding rocket campaign are critically examined alongside complementary numerical simulations. Particular processes of interest include cavity formation due to intense frictional heating and Pedersen drifts, evolution in the presence of structured precipitation, and refilling due to impact ionization and downflows. Our analysis uses an ionospheric fluid model which solves conservation of mass, momentum, and energy equations for all major ionospheric species. These fluid equations are coupled to an electrostatic current continuity equation to self-consistently describe auroral electric fields. Energetic electron precipitation inputs for the model are specified by inverting optical data, and electric field boundary conditions are obtained from direct PFISR measurements. Thus, the model is driven in as realistic a manner as possible. Both ISR data and simulations indicate that the conversion of the F-region plasma to molecular ions and subsequent recombination is the dominant process contributing to the formation of the observed cavities, all of which occur in conjuction with electric fields exceeding ∼ 90 mV/m. Furthermore, the cavities often persist several minutes past the point when the frictional heating stops. Impact ionization and field-aligned plasma flows modulate the cavity depth in a significant way, but are of secondary importance to the molecular generation process. Informal comparisons of the ISR density and temperature fits to the model verify that the simulations reproduce most of the observed cavity features to a reasonable level of detail.

Description: Energetic particle injections in the near-Earth plasma sheet are critical for supplying particles and energy to the inner magnetosphere. Recent case studies have demonstrated a good correlation between injections and transient, narrow, fast flow channels as well as earthward reconnection (dipolarization) fronts in the magnetotail, but statistical observations beyond geosynchronous orbit (GEO) to verify the findings were lacking. By surveying trans-geosynchronous injections using THEMIS, we show that their likely origin is the earthward-traveling, dipolarizing flux bundles following near-Earth reconnection. The good correlation between injections and fast flows, reconnection fronts and impulsive, dawn-dusk electric field increases is not limited to within 12 R E , but extends out to 30 R E . Like near-Earth reconnection, both ion and electron injections are most probable in the pre-midnight sector. Similar to bursty bulk flows (BBFs), injection-time flow speeds are faster with increasing distance from Earth. With faster flows, injection intensity generally increases and extends to higher energy channels. With increased geomagnetic activity, injection occurrence rate increases (akin to that of BBFs) and spectral hardening occurs (κ decreases). The occurrence rate increase within the inner magnetosphere suggests that injections populate the radiation belts more effectively under enhanced geomagnetic activity. Our results are inconsistent with the classical concept of an azimuthally wide injection boundary moving earthward from ~9-12 R E to GEO under an enhanced cross-tail electric field. Rather, particle injection and transport occur along a large range of radial distances due to effects from earthward-penetrating, azimuthally localized, transient, strong electric fields of recently reconnected, dipolarizing flux bundles.

Description: A method for estimating the vector neutral wind profiles in the mesosphere and lower thermosphere (MLT) region of the upper atmosphere from Arecibo dual-beam incoherent scatter radar data is presented. The method yields continuous estimates of both the altitude-averaged F -region plasma drifts and all three components of the altitude-resolved neutral wind profiles in the MLT using data taken while the Arecibo feed system swings in azimuth. The problem is mixed determined, and its solution is not inherently unique. Second order Tikhonov regularization is used to find solutions consistent with the available data while being minimally structured, additional structure being unsupported by the data. The solution is found using the method of conjugate gradient least squares and sparse matrix mathematics. Example data acquired during an interval of midlatitude spread F are used to illustrate the method. The estimated wind profiles exhibit characteristics broadly consistent with gravity waves but are impulsive, with features that generally persist for less than one and a half wave periods.

Description: Inland waters were recently recognized to be important sources of methane (CH 4 ) and carbon dioxide (CO 2 ) to the atmosphere, and including inland water emissions in large scale greenhouse gas (GHG) budgets may potentially offset the estimated carbon sink in many areas. However, the lack of GHG flux measurements and well-defined inland water areas for extrapolation, make the magnitude of the potential offset unclear. This study presents coordinated flux measurements of CH 4 and CO 2 in multiple lakes, ponds, rivers, open wells, reservoirs, springs, and canals in India. All these inland water types, representative of common aquatic ecosystems in India, emitted substantial amounts of CH 4 and a major fraction also emitted CO 2 . The total CH 4 flux (including ebullition and diffusion) from all the 45 systems ranged from from 0.01 to 52.1 mmol m −2 d −1 , with a mean of 7.8 ± 12.7 (mean ± 1SD) mmol m −2 d −1 . The mean surface water CH 4 concentration was 3.8 ± 14.5 μ M (range 0.03 to 92.1 μ M). The CO 2 fluxes ranged from -28.2 to 262.4 mmol m −2 d −1 and the mean flux was 51.9 ± 71.1 mmol m −2 d −1 . The mean partial pressure of CO 2 was 2927 ± 3269 μ atm (range - 400 to 11467 μ atm). Conservative extrapolation to whole India, considering the specific area of the different water types studied, yielded average emissions of 2.1 Tg CH 4 yr −1 and 22.0 Tg CO 2 yr −1 from India's inland waters. When expressed as CO 2 equivalents, this amounts to 75 Tg CO 2 equivalents yr −1 (53 – 98 Tg CO 2 equivalents yr −1 ; ± 1SD) , with CH 4 contributing 71%. Hence, average inland water GHG emissions, which were not previously considered, correspond to 42% (30 – 55%) of the estimated land carbon sink of India. Thereby this study illustrates the importance of considering inland water GHG exchange in large scale assessments. This article is protected by copyright. All rights reserved.

Description: ‘Blue Carbon’, which is carbon captured by marine living organisms, has recently been highlighted as a new option for climate change mitigation initiatives. In particular, coastal ecosystems have been recognized as significant carbon stocks because of their high burial rates and long-term sequestration of carbon. However, the direct contribution of Blue Carbon to the uptake of atmospheric CO 2 through air-sea gas exchange remains unclear. We performed in situ measurements of carbon flows, including air-sea CO 2 fluxes, dissolved inorganic carbon changes, net ecosystem production, and carbon burial rates in the boreal (Furen), temperate (Kurihama), and subtropical (Fukido) seagrass meadows of Japan from 2010 to 2013. In particular, the air-sea CO 2 flux was measured using three methods: the bulk formula method, the floating chamber method, and the eddy covariance method. Our empirical results show that submerged autotrophic vegetation in shallow coastal waters can be functionally a sink for atmospheric CO 2. This finding is contrary to the conventional perception that most near-shore ecosystems are sources of atmospheric CO 2 . The key factor determining whether or not coastal ecosystems directly decrease the concentration of atmospheric CO 2 may be net ecosystem production. This study thus identifies a new ecosystem function of coastal vegetated systems; they are direct sinks of atmospheric CO 2 .

Description: We report the peculiar interaction of two type III bursts observed in the solar wind. As electrons beams propagating on the same magnetic field lines cross, a spectacular depletion of the type III radio emission is observed. We combine observations from the WAVES experiment on board the STEREO mission together with kinetic plasma simulations to study the extinction of type III radio emission resulting from the interaction between two electron beams. The remote observations enable to follow the electron beams in the interplanetary medium and show that the level of radiated radio waves is recovered after the beam crossing. The in situ observations of beam-driven Langmuir waves give evidence for Langmuir decay. The density fluctuations are extracted from in situ observations. The velocity of the beams is independently evaluated from in situ observations of decaying Langmuir waves and remote radio observations. The kinetic simulations show that the level of beam-driven Langmuir waves is reduced as the two beams cross. We show that the slow beam induced a strong reduction of the quasilinear relaxation of the fast beam, limiting the amplitude of the generated Langmuir waves. Moreover, in the case of two electron beams, the lack of Langmuir waves coherence reduces the efficiency of the Langmuir parametric decay. We thus conclude that the observed depletion of the type III radio 5 is independent of the radio emission mechanism, as long as it depends on the Langmuir amplitude and coherence.

Description: The solar minimum period between solar cycles 23 and 24 was the longest since the beginning of space-based measurements, and many manifestations of solar activity were unusually low. Thermospheric neutral density was about 30% lower than during the previous solar minimum, but changes in the ionosphere between the two solar minima are more controversial. Solar radiation, geomagnetic activity, and anthropogenic increases in greenhouse gases, can all play a role in these changes. In this paper, we address the latter of these potential contributions, the degree to which secular change driven by greenhouse gases, primarily CO 2 , could be responsible for the observed changes. New 3D model simulations find a global mean density decrease at 400 km of 5.8% between the two recent solar minima, which is larger than earlier 1D model results, and in better agreement with observations. From these model simulations and from other observational work, we estimate that the contribution of secular change to global mean neutral density decrease between the two recent solar minima is less than ~6%. The contribution of secular change to the global average decrease of F-region ionosphere peak density ( N m F 2 ) and altitude ( h m F 2 ), near mid-day, is estimated to be 1.5% and 1.5 km, respectively. However, secular changes in the ionosphere exhibit large variations with local time, geographic location, and season. The mid-day change of N m F 2 seen in the model simulations ranged between +6% and -9%, and the change of h m F 2 ranged between +11 km and -11 km, depending on geographic location.

Description: In this paper we study the planetary magnetic disturbance during the magnetic storm occurring on 05 April 2010 associated with high speed solar wind stream due to a coronal hole following a CME. We separate the magnetic disturbance associated to the ionospheric disturbance dynamo (Ddyn) from the magnetic disturbance associated to the prompt penetration of magnetospheric electric field (DP2). This event exhibits different responses of ionospheric disturbance dynamo in the different longitude sectors (European-African, Asian and American). The strongest effect is observed in the European-African sector. The Ddyn disturbance reduces the amplitude of the daytime H-component at low latitudes during four consecutive days in agreement with the Blanc and Richmond's model of ionospheric disturbance dynamo. The amplitude of Ddyn decreased with time during the four days. We discuss its diverse worldwide effects. The observed signature of magnetic disturbance process in specific longitude sector is strongly dependent on which Earth's side faces the magnetic storms (i.e., there is a different response depending on which longitude sector is at noon when the SSC hits).Finally we determined an average period of 22 hours for Ddyn using wavelet analysis.

Description: Complex magnetosphere-ionosphere coupling mechanisms result in high latitude irregularities that are difficult to characterize using only Global Navigation Satellite System (GNSS) scintillation measurements. However, GNSS observations combined with physical parameters derived from modeling can be used to study the physics of these irregularities. We have developed a full three dimensional (3D) electromagnetic (EM) wave propagation model called “Satellite-beacon Ionospheric-scintillation Global Model ofthe upper Atmosphere" (SIGMA), to simulate GNSS scintillations. This model eliminates the most significant approximation made by the previous simulation approaches about the correlation length of the irregularity. Thus, for the first time, using SIGMA wecan accomplish scintillation simulations of significantly high fidelity. While the model is global, it is particularly applicable at high latitudes as it accounts for the complicated geometry of the magnetic field lines in these regions. Using SIGMA wesimulate the spatial and temporal variations in the GNSS signal phase and amplitude on the ground. In this paper, we present the model and results from a study to determine the sensitivity of the SIGMA outputs to different input parameters. We have deduced from our sensitivity study that the peak to peak (P2P) power gets most affected by the spectral index and line of sight (LOS) direction, while the P2P phase and standard deviation of the phase ( σ φ ) are more sensitive to the anisotropy of the irregularity. The sensitivity study of SIGMA narrows the parametric space to investigate when comparing the modeled results to the observations.

Description: The attenuation of VLF signals from lightning and ground-based VLF transmitters during transionospheric propagation has been the subject of recent interest, as discrepancies have been found between satellite data and model calculations. Previous modeling efforts, however, have not considered the self-absorption effect due to nonlinear heating and ionization in the lower ionosphere. A self-consistent model of ionospheric heating is presented here using a time-domain model of VLF wave propagation through the ionosphere. The model is able to estimate the attenuation of signals due to heating below ~100 km altitude. In this model, the ionospheric state is updated as the fields propagate, leading to changes in collision frequency and electron density, which in turn affect the wave propagation. We use this model for ground-based VLF transmitters at different frequencies, amplitudes, and latitudes (i.e., magnetic dip angle), and for lightning-generated sferics with different amplitudes, at different latitudes, and using a variety of ionospheric density profiles. We find that the inclusion of self-consistent heating causes a change in the transionospherically propagating wave amplitude that varies considerably with the source amplitude and other parameters. Typical values for the heating contribution to wave attenuation are 1-2 dB for VLF transmitters, but greater than 10 dB for large amplitude lightning discharges. An interesting effect is observed for VLF transmitters and low-amplitude lightning, where the signal is actually enhanced due to heating, rather than attenuated, in the direction propagating across the Earth's magnetic field.

Description: Land Surface Phenology (LSP) is the most direct representation of intra-annual dynamics of vegetated land surfaces as observed from satellite imagery. LSP plays a key role in characterizing land-surface fluxes, and is central to accurately parameterizing terrestrial biosphere–atmosphere interactions, as well as climate models. In this paper we present an evaluation of Pan-European LSP and its changes over the past 30 years, using the longest continuous record of Normalized Difference Vegetation Index (NDVI) available to date in combination with a landscape-based aggregation scheme. We used indicators of Start-Of-Season, End-Of-Season and Growing Season Length (SOS, EOS and GSL, respectively) for the period 1982–2011 to test for temporal trends in activity of terrestrial vegetation and their spatial distribution. We aggregated pixels into ecologically representative spatial units using the European Landscape Classification (LANMAP) and assessed the relative contribution of spring and autumn phenology. GSL increased significantly by 18–24 days/decade over 18–30% of the land area of Europe, depending on methodology. This trend varied extensively within and between climatic zones and landscape classes. The areas of greatest growing-season lengthening were the Continental and Boreal zones, with hotspots concentrated in southern Fennoscandia, Western Russia and pockets of continental Europe. For the Atlantic and Steppic zones, we found an average shortening of the growing season with hotspots in Western France, the Po valley, and around the Caspian Sea. In many zones, changes in the NDVI-derived end-of-season contributed more to the GSL trend than changes in spring green-up, resulting in asymmetric trends. This underlines the importance of investigating senescence and its underlying processes more closely as a driver of LSP and global change. This article is protected by copyright. All rights reserved.

Description: Understanding the responses of terrestrial ecosystems to global change remains a major challenge of ecological research. We exploited a natural elevation gradient in a northern hardwood forest to determine how reductions in snow accumulation, expected with climate change, directly affect dynamics of soil winter frost, and indirectly soil microbial biomass and activity during the growing season. Soils from lower elevation plots, which accumulated less snow and experienced more soil temperature variability during the winter (and likely more freeze/thaw events), had less extractable inorganic nitrogen (N), lower rates of microbial N production via potential net N mineralization and nitrification, and higher potential microbial respiration during the growing season. Potential nitrate production rates during the growing season were particularly sensitive to changes in winter snow pack accumulation and winter soil temperature variability, especially in spring. Effects of elevation and winter conditions on N transformation rates differed from those on potential microbial respiration, suggesting that N-related processes might respond differently to winter climate change in northern hardwood forests than C-related processes. This article is protected by copyright. All rights reserved.

Description: The present work has investigated the configuration of field-aligned currents (FACs) during a long period of radial interplanetary magnetic field (IMF) on 19 May 2002 by using high-resolution and precise vector magnetic field measurements of the CHAMP satellite. During the interest period IMF B y and B z are weakly positive and B x keeps pointing to the Earth for almost 10 hours. The geomagnetic indices Dst is about -40 nT and AE about 100 nT on average. The cross polar cap potential calculated from Assimilative Mapping of Ionospheric Electrodynamics and derived from DMSP observations have average values of 10-20 kV. Obvious hemispheric differences are shown in the configurations of FACs on the day and nightside. At the south pole FACs diminish in intensity to magnitudes of about 0.1  μA/m 2 , the plasma convection maintains two cell flow pattern, and the thermospheric density is quiet low. However, there are obvious activities in the northern cusp region. One pair of FACs with a downward leg toward the pole and upward leg on the equatorward side emerge in the northern cusp region, exhibiting opposite polarity to FACs typical for duskward IMF orientation. An obvious sunward plasma flow channel persists during the whole period. These ionospheric features might be manifestations of an efficient magnetic reconnection process occurring in the northern magnetospheric flanks at high latitude. The enhanced ionospheric current systems might deposit large amount of Joule heating into the thermosphere. The air densities in the cusp region get enhanced and subsequently propagate equatorward on the dayside. Although geomagnetic indices during the radial IMF indicate low level activity, the present study demonstrates that there are prevailing energy inputs from the magnetosphere to both the ionosphere and thermosphere in the northern polar cusp region.

Description: The interaction of planetary bodies with their surrounding magnetized plasma can often be described with the magneto-hydrodynamic (MHD) equations, which are commonly solved by numerical models. For these models it is necessary to define physically correctboundary conditions for the plasma mass and energy density, the plasma velocity and the magnetic field. Many planetary bodies have electrically non-conductive surfaces, which do not allow electric current to penetrate their surfaces. Magnetic boundary conditions, which consider that the associated radial electric current at the planetary surface is zero are difficult to implement because they include the curl of the magnetic field. Here we derive new boundary conditions by a decomposition of the magnetic field in poloidal and toroidal parts. We find that the toroidal part of the magnetic field needs to vanish at the surface of the insulator. For the spherical harmonics coefficients of the poloidal part we derive a Cauchy boundary condition, whichalso matches a possible intrinsic field by including its Gauss coefficients. Thus we can additionally include planetary dynamo fields as well as time-variable induction fields within electrically conductive subsurface layers. We implement the non-conducting boundary condition in the MHD simulation code ZEUS-MP using spherical geometry and provide a numerical implementation in Fortran 90 as auxiliary-material on the JGR website. We apply it to a model for Ganymede's plasma environment. Our model also includes a consistent set of boundary conditions for the other MHD variables density, velocity and energy. With this model we can describe Galileo spacecraft observations in and around Ganymede's mini-magnetosphere very well.

Description: In recent years we have benefitted greatly from the first in-orbit multi-wavelength images of Saturn's polar atmosphere from the Cassini spacecraft. Specifically, images obtained from the Cassini UltraViolet Imaging Spectrograph (UVIS) provide an excellent view of the planet's auroral emissions, which in turn give an account of the large-scale magnetosphere-ionosphere coupling and dynamics within the system. However, obtaining near-simultaneous views of the auroral regions with in situ measurements of magnetic field and plasma populations at high-latitudes is more difficult to routinely achieve. Here we present an unusual case, during Revolution 99 in January 2009, where UVIS observes the entire northern UV auroral oval during a two-hour interval while Cassini traverses the magnetic flux tubes connecting to the auroral regions near 21 LT, sampling the related magnetic field, particle, and radio and plasma wave signatures. The motion of the auroral oval evident from the UVIS images requires a careful interpretation of the associated latitudinally “oscillating” magnetic field and auroral field-aligned current signatures whereas previous interpretations have assumed a static current system. Concurrent observations of the auroral hiss (typically generated in regions of downward directed field-aligned current) support this revised interpretation of an oscillating current system. The nature of the motion of the auroral oval evident in the UVIS image sequence, and the simultaneous measured motion of the field-aligned currents (and related plasma boundary) in this interval, is shown to be related to the northern hemisphere magnetosphere oscillation phase. This is in agreement with previous observations of the auroral oval oscillatory motion.

Description: We have developed a technique by which to estimate the spatial distribution of plasmaspheric helium ions based on extreme ultraviolet (EUV) data obtained from the IMAGE satellite. The estimation is performed using a linear inversion method based on the Bayesian approach. The global imaging data from the IMAGE satellite enables us to estimate a global two-dimensional distribution of the helium ions in the plasmasphere. We applied this technique to a synthetic EUV image generated from a numerical model. This technique was confirmed to successfully reproduce the helium ion density that generated the synthetic EUV data. We also demonstrate how the proposed technique works for real data using two real EUV images.

Description: Development efforts for poverty reduction and food security in sub-Saharan Africa will have to consider future climate change impacts. Large uncertainties in climate change impact assessments do not necessarily complicate, but can inform development strategies. The design of development strategies will need to consider the likelihood, strength, and interaction of climate change impacts across biosphere properties. We here explore the spread of climate change impact projections and develop a composite impact measure to identify hotspots of climate change impacts, addressing likelihood and strength of impacts. Overlapping impacts in different biosphere properties (e.g. flooding, yields) will not only claim additional capacity to respond, but will also narrow the options to respond and develop. Regions with severest projected climate change impacts often coincide with regions of high population density and poverty rates. Science and policy need to propose ways of preparing these areas for development under climate change impacts.

Description: We use cosmic radiation records (neutron monitor and the cosmogenic radionuclides, 10 Be and 14 C) as a proxy to compare the solar activity during the extended solar minimum 2006-9, with that during the Grand Solar Minima and Maxima that occurred between 1391-2010. The inferred cosmic ray intensities during the Spoerer, Maunder, and Dalton Grand Minima were significantly greater than those during 2006-9. The onset phases of the three Grand Minima extended over between two and five Schwabe (sunspot) cycles, the cosmic ray intensity at the Schwabe minima increasing from a value approximating that of 2006-9, to substantially higher values later in the Grand Minimum. The minimum estimated strengths of the heliospheric magnetic field near Earth during the Grand Minima were 2.4nT (Spoerer); 〈2.0nT(Maunder) and 2.6 nT (Dalton), compared to 3.9nT in 2009. We conclude that the periods of highest solar activity during the Maunder Minimum approximated those near the sunspot minima between 1954 and 1996. The average ratio of the maximum to minimum estimated HMF in the six Schwabe cycles in the Maunder Minimum is 1.54 (range 1.30-1.85) compared to 1.52 (1.31-1.63) for the modern epoch suggesting similar operation of the solar dynamo in both intervals. The onset phase of the Maunder Minimum extending over five Schwabe cycles, and the large increase in cosmic ray flux (and decrease in estimated heliospheric magnetic field), leads us to speculate that the magnetohydrodynamic amplification in the solar dynamo exhibits a relaxation time well in excess of the 11 year period of the Schwabe cycle.

Description: The temperature profile obtained from the space borne instrument ‘Sounding of Atmosphere by Broadband Emission Radiometry’ (SABER) instrument onboard ‘Thermosphere Ionosphere Mesosphere Energetics and Dynamics’ (TIMED) shows a triple layered mesospheric inversion event on the night of 23 September 2011, when there is an overpass near the low-latitude sites Gadanki (13.5°N, 79.2°E) and Tirunelveli (8.7°N, 77.8°E). The three mesospheric inversion layers (MIL) are formed in the height region around ~70 km (lower), ~80 km (middle) and ~90 km (upper) with amplitudes ~11 K, ~44 K, and ~109 K and thickness of 3.4 km, 4.9 km and 6.6 km respectively. The formation of the lower and middle MILs can only be observed in the Rayleigh lidar temperature profiles over Gadanki due to upper height limitation of the system. Nearly all the dominant causative mechanisms are examined for the occurrence of the MIL event. The lower MIL at ~70 km is inferred to be due to planetary wave dissipation, as there is a sudden decrease of planetary wave activity above 70 km. Further, it is demonstrated that the middle MIL at ~80 km is due to the turbulence generated by gravity wave breaking which is in turn due to gravity wave–semi-diurnal tidal interaction, though the height of the middle MIL descends at the rate of ~1 km/h, which is nearly the vertical phase speed of diurnal tide, whereas the upper MIL at above 90 km is due to the large chemical heating rate (~45 K/day) generated by the dominant exothermic reaction O + O + M → O 2  + M.

Description: In this paper, we analyze radar observations of E x B drift and plasma irregularities, ionosonde observations of E- and F-layer parameters including spread F, and magnetic field observations made from Indian low latitudes linked with the 2009 sudden stratospheric warming (SSW) event. E x B drift variations presented here are the first of their kind from the Indian sector as far as the effect of SSW is concerned. Difference of magnetic fields observed from the equator and low latitude (∆H) and E x B drift show linear relation and both show remarkably large positive values in the morning and negative values in the afternoon exhibiting semidiurnal behavior. Remarkable changing patterns in the critical frequency of F 2 layer (f o F 2 ) and F 3 layer (f o F 3 ) were observed after the occurrence of SSW. Large variations with quasi-16-day periodicity were observed in ∆H, f o F 2 and f o F 3. Both semidiurnal and quasi-16-day wave modulation observed after the 2009 SSW event are consistent with those reported earlier. We also noted quasi-6 day variations in ∆H and f o F 2 soon after the SSW commencement, not much reported before. During the counter-electrojet events linked with the SSW event, while equatorial E s (E sq ) disappeared as expected, there were no blanketing E s (E sb ), a finding not reported and discussed earlier. E sb was also not formed at the off-equatorial location, indicating the absence of required vertical wind shear, but E region plasma irregularities were observed by the ionosonde and radar with a close relationship between the two. Weak F region irregularities were observed in the post-midnight hours and case studies suggest the possible role of SSW related background electric field in the manifestation of post-midnight F region irregularities.

Description: The Defense Meteorological Satellite Program (DMSP) launches and maintains a network of satellites to monitor the meteorological, oceanographic, and solar-terrestrial physics environments. In the past decade, geomagnetic field modelers have focused much attention on magnetic measurements from missions such as CHAMP, Ørsted and SAC-C. With the completion of the CHAMP mission in 2010, there has been a multi-year gap in satellite-based vector magnetic field measurements available for main field modeling. In this study, we calibrate the Special Sensor Magnetometer (SSM) instrument onboard DMSP to create a dataset suitable for main field modeling. These vector field measurements are calibrated to compute instrument timing shifts, scale factors, offsets, and non-orthogonality angles of the fluxgate magnetometer cores. Euler angles are then computed to determine the orientation of the vector magnetometer with respect to a local coordinate system. We fit a degree 15 main field model to the dataset and compare with the World Magnetic Model (WMM) and Ørsted scalar measurements. We call this model DMSP-MAG-1 and its coefficients and software are available for download at http://geomag.org/models/dmsp.html . Our results indicate that the DMSP dataset will be a valuable source for main field modeling for the years between CHAMP and the recently launched Swarm mission.

Description: Established forests currently function as a major carbon sink, sequestering as woody biomass about 26% of global fossil fuel emissions. Whether forests continue to act as a global sink will depend on many factors, including the response of aboveground wood production (AWP; MgC ha -1 yr -1 ) to climate change. Here we explore how AWP in New Zealand's natural forests is likely to change. We start by statistically modelling the present-day growth of 97,361 individual trees within 1070 permanently marked inventory plots as a function of tree size, competitive neighbourhood and climate. We then use these growth models to identify the factors that most influence present-day AWP and to predict responses to medium-term climate change under different assumptions. We find that if the composition and structure of New Zealand's forests were to remain unchanged over the next 30 years, then AWP would increase by 6–23%, primarily as a result of physiological responses to warmer temperatures (with no appreciable effect of changing rainfall). However, if warmth-requiring trees were able to migrate into currently cooler areas and if denser canopies were able to form, then a different AWP response is likely: forests growing in the cool mountain environments would show a 30% increase in AWP whilst those in the lowland would hardly respond (on average, -3% when mean annual temperature exceeds 8.0 ° C). We conclude that response of wood production to anthropogenic climate change is not only dependent on the physiological responses of individual trees, but is highly contingent on whether forests adjust in composition and structure. This article is protected by copyright. All rights reserved.

Description: Cleaning symbioses play an important role in the health of certain coastal marine communities. These interspecific associations often occur at specific sites (cleaning stations) where a cleaner organism (commonly a fish or shrimp) removes ectoparasites/damaged tissue from a “client” (a larger cooperating fish). At present, the potential impact of climate change on the fitness of cleaner organisms remains unknown. The present study investigated the physiological and biochemical responses of tropical ( Lysmata amboinensis ) and temperate ( L. seticaudata ) cleaner shrimp to global warming. Specifically, thermal limits (CTMax), metabolic rates, thermal sensitivity, heat shock response (HSR), lipid peroxidation [malondialdehyde (MDA) concentration], lactate levels, antioxidant (GST, SOD and catalase) and digestive enzyme activities (trypsin and alkaline phosphatase) at current and warming (+ 3 °C) temperature conditions. In contrast to temperate species, CTMax values decreased significantly from current (24 – 27 °C) to warming temperature conditions (30 °C) for the tropical shrimp, where metabolic thermal sensitivity was affected and the HSR was significantly reduced. MDA levels in tropical shrimp increased dramatically, indicating extreme cellular lipid peroxidation, which was not observed in the temperate shrimp. Lactate levels, GST and SOD activities were significantly enhanced within the muscle tissue of the tropical species. Digestive enzyme activities in the hepatopancreas of both species were significantly decreased by warmer temperatures. These data suggested tropical cleaner shrimp were less able to acclimatize and would be more vulnerable to global warming than temperate species like Lysmata seticaudata which evolved in a relatively unstable environment with seasonal thermal variations that may have conferred greater adaptive plasticity. This indicated tropical cleaning symbioses may be challenged by warming-related anthropogenic forcing, with potential cascading effects on the health and structuring of tropical coastal communities (e.g., coral reefs). This article is protected by copyright. All rights reserved.

Description: Despite decades of research, how climate warming alters the global flux of soil respiration is still poorly characterized. Here, we use meta-analysis to synthesize 202 soil respiration datasets from 50 ecosystem warming experiments across multiple terrestrial ecosystems. We found that, on average, warming by 2 °C increased soil respiration by 12% during the early warming years, but warming-induced drought partially offset this effect. More significantly, the two components of soil respiration, heterotrophic respiration and autotrophic respiration, showed distinct responses. The warming effect on autotrophic respiration was not statistically detectable during the early warming years, but nonetheless decreased with treatment duration. In contrast, warming by 2 °C increased heterotrophic respiration by an average of 21%, and this stimulation remained stable over the warming duration. This result challenged the assumption that microbial activity would acclimate to the rising temperature. Together, our findings demonstrate that distinguishing heterotrophic respiration and autotrophic respiration would allow us better understand and predict the long-term response of soil respiration to warming. The dependence of soil respiration on soil moisture condition also underscores the importance of incorporating warming-induced soil hydrological changes when modeling soil respiration under climate change. This article is protected by copyright. All rights reserved.

Description: Understanding how copepods may respond to ocean acidification (OA) is critical for risk assessments of ocean ecology and biogeochemistry. The perception that copepods are insensitive to OA is largely based on experiments with adult females. Their apparent resilience to increased carbon dioxide (pCO 2 ) concentrations has supported the view that copepods are ‘winners’ under OA. Here, we show that this conclusion is not robust, that sensitivity across different life stages is significantly misrepresented by studies solely using adult females. Stage-specific responses to pCO 2 (385–6000 μatm) were studied across different life stages of a calanoid copepod, monitoring for lethal and sublethal responses. Mortality rates varied significantly across the different life stages, with nauplii showing the highest lethal effects; nauplii mortality rates increased threefold when pCO 2 concentrations reached 1000 μatm (year 2100 scenario) with LC 50 at 1084 μatm pCO 2 . In comparison, eggs, early copepodite stages, and adult males and females were not affected lethally until pCO 2 concentrations ≥3000 μatm. Adverse effects on reproduction were found, with 〉35% decline in nauplii recruitment at 1000 μatm pCO 2 . This suppression of reproductive scope, coupled with the decreased survival of early stage progeny at this pCO 2 concentration, has clear potential to damage population growth dynamics in this species. The disparity in responses seen across the different developmental stages emphasizes the need for a holistic life-cycle approach to make species-level projections to climate change. Significant misrepresentation and error propagation can develop from studies which attempt to project outcomes to future OA conditions solely based on single life history stage exposures.

Description: Identifying the type and strength of interactions between local anthropogenic and other stressors can help to set achievable management targets for degraded marine ecosystems and support their resilience by identifying local actions. We undertook a meta-analysis, using data from 118 studies to test the hypothesis that ongoing global declines in the dominant habitat along temperate rocky coastlines, forests of canopy-forming algae and/or their replacement by mat-forming algae are driven by the non-additive interactions between local anthropogenic stressors that can be addressed through management actions (fishing, heavy metal pollution, nutrient enrichment and high sediment loads) and other stressors (presence of competitors or grazers, removal of canopy algae, limiting or excessive light, low or high salinity, increasing temperature, high wave exposure, and high UV or CO 2 ), not as easily amenable to management actions. In general, the cumulative effects of local anthropogenic and other stressors had negative effects on the growth and survival of canopy-forming algae. Conversely, the growth or survival of mat-forming algae was either unaffected or significantly enhanced by the same pairs of stressors. Contrary to our predictions, the majority of interactions between stressors were additive. There were however synergistic interactions between nutrient enrichment and heavy metals, the presence of competitors, low light, and increasing temperature, leading to amplified negative effects on canopy-forming algae. There were also synergistic interactions between nutrient enrichment and increasing CO 2 and temperature leading to amplified positive effects on mat-forming algae. Our review of the current literature shows that management of nutrient levels, rather than fishing, heavy metal pollution or high sediment loads, would provide the greatest opportunity for preventing the shift from canopy to mat-forming algae, particularly in enclosed bays or estuaries because of the higher prevalence of synergistic interactions between nutrient enrichment with other local and global stressors, and as such it should be prioritised. This article is protected by copyright. All rights reserved.

Description: Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database of approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general controls on wetland methane emissions from soil temperature, water table, and vegetation, but also show that these relationships are modified depending on wetland type (bog, fen, or swamp), region (subarctic to temperate), and disturbance. Fen methane flux was more sensitive to vegetation and less sensitive to temperature than bog or swamp fluxes. The optimal water table for methane flux was consistently below the peat surface in bogs, close to the peat surface in poor fens, and above the peat surface in rich fens. However, the largest flux in bogs occurred when dry 30-day averaged antecedent conditions were followed by wet conditions, while in fens and swamps, the largest flux occurred when both 30-day averaged antecedent and current conditions were wet. Drained wetlands exhibited distinct characteristics, e.g. the absence of large flux following wet and warm conditions, suggesting that the same functional relationships between methane flux and environmental conditions cannot be used across pristine and disturbed wetlands. Together, our results suggest that water table and temperature are dominant controls on methane flux in pristine bogs and swamps, while other processes, such as vascular transport in pristine fens, have the potential to partially override the effect of these controls in other wetland types. Because wetland types vary in methane emissions and have distinct controls, these ecosystems need to be considered separately to yield reliable estimates of global wetland methane release.

Description: [1]  Jupiter's large scale size and rapid planetary rotation period combine to produce the strong centrifugal force responsible for many unique properties of its magnetosphere. It was previously proposed that this centrifugal force and non-adiabatic field line stretching could cause the observed dawn-dusk asymmetry of Jupiter's plasma sheet, which is thickest near dusk. As flux tubes rotate and stretch between noon and dusk, particles bouncing along the field gain parallel energy and create pressure anisotropy. Because bounce times can be long compared with the outward expansion timescale, particles may respond non-adiabatically, and the resulting pressure anisotropy can drive the plasma sheet to instability. We used a large-scale kinetic (LSK) simulation to follow a collection of rotating particles as they move in a time-varying, rotating magnetic field designed to represent flux tube expansion in Jupiter's magnetosphere. The analysis quantifies the response of trapped particles by characterizing the pressure anisotropy and energy changes. We compare results of non-adiabatic and adiabatic outward expansion, and find that the non-adiabatic case leads to a large pitch angle anisotropy and higher total energy than for adiabatic expansion. Although the calculation was not handled fully self-consistently, the results support the proposition that plasma pressure changes lead to changes in the magnetic field structure with local time. Our findings are consistent with the idea that non-adiabatic effects in Jupiter's magnetosphere contribute to field dipolarization and the observed plasma sheet thickening between noon and dusk.

Description: [1]  The IMAGE network magnetic measurements during the period 1995-2009 (covering the whole of solar cycle 23) are used to characterize the annual variations in the westward electrojet. The results suggest that the annual variations in different local time sector are quite different due to the different sources. In the MLT-sector 2200-0100, the annual variations with maxima in winter suggest they are caused by the combined effects of the convective electric field and the conductivity associated with particle precipitation. Furthermore, the conductivity seems to play a more important role in the MLT-sector ~2200-2320, while the convective electric field appears to be more important in the MLT-sector ~2320-0100. In the MLT-sector 0300-0600, the annual variations with maxima in summer suggest they are caused by solar EUV conductivity effect and the equinoctial effect, which work in two fundamentally different ways. The solar EUV conductivity effect works by increasing ionospheric conductivity and enhancing the westward electrojet in summer, while the equinoctial effect works by decreasing solar wind-magnetosphere coupling efficiency and weakening the westward electrojet in winter. In the MLT-sector 0100-0300, the annual variations are relatively weak, and can be attributed to the combined effects of annual variations caused by all the previously mentioned effects. In addition, we find that a significant annual variation in substorm occurrence rate, mainly occurring in the premidnight region, is quite similar to that in the westward electrojet. We suggest that elevated solar wind driving during the winter months contributes to higher substorm occurrence in winter in the Northern Hemisphere.

Description: No abstract is available for this article.

Description: Chorus waves play an important role in energetic electron dynamics in the inner magnetosphere. In this work, we present a new hybrid code, DAWN, to simulate the generation of chorus waves. The DAWN code is unique in that it models cold electrons using linearized fluid equations and hot electrons using particle-in-cell techniques. The simplified fluid equations can be solved with robust and simple algorithms. We demonstrate that discrete chorus elements can be generated using the code. Waveforms of the generated element show amplitude modulation or “subpackets”, and the frequency sweep rate of the generated element is found to be consistent with that of observed chorus waves. Using the DAWN code, we then investigate the variation of wave intensity with respect to linear growth rates on the equatorial plane. Previous observations showed that the change in linear growth rates of whistler waves modulated by external processes such as density modulations is usually small , while the variation of the wave intensity is large . Using a chosen set of background plasma parameters, we demonstrate that a small change in linear growth rates can lead to significant variation of wave intensity only in the transition from the broadband whistler wave generation regime to the chorus wave generation regime. Our results demonstrate the importance of including nonlinear dynamics of chorus generation in understanding the whistler wave intensity modulation process in the inner magnetosphere.

Description: We report the observation of echo extreme horizontal drift speed (EEHS, ≥ 300 m s -1 ) during polar mesospheric (80-90 km) summer echoes (PMSEs) by the VHF (52-MHz) radar at Esrange, Sweden, in years of 2006 and 2008. The EEHS occur in PMSEs as correlated with high-speed solar wind streams (HSSs), observed at least once in 12-17 % of all hours of observation for the two summers. The EEHS rate peaks occur either during high solar wind speed in the early part of the PMSE season or during the arrival of interplanetary corotating interaction regions (CIRs) followed by peaks in PMSE occurrence rate after 1-4 days, in the latter part of the 2006 summer. The cause of EEHS rate peaks is likely under the competition between the interval of the CIR and HSS passage over the magnetosphere. A candidate process in producing EEHS is suggested to be localized strong electric field, which is caused by solar wind energy transfer from the interaction of CIR and HSS with the magnetosphere in a sequential manner. We suggest that EEHS are created by strong electric field, estimated as 〉 10-30 V m -1 at 85 km altitude, exceeding the mesospheric breakdown threshold field.

Description: Increased nitrogen (N) depositions expected in the future endanger the diversity and stability of ecosystems primarily limited by N, but also often co-limited by other nutrients like phosphorus (P). In this context a nutrient manipulation experiment (NUMEX) was set up in a tropical montane rainforest in southern Ecuador, an area identified as biodiversity hotspot. We examined impacts of elevated N and P availability on arbuscular mycorrhizal fungi (AMF), a group of obligate biotrophic plant symbionts with an important role in soil nutrient cycles. We tested the hypothesis that increased nutrient availability will reduce AMF abundance, reduce species richness and shift the AMF community towards lineages previously shown to be favored by fertilized conditions. NUMEX was designed as a full factorial randomized block design. Soil cores were taken after two years of nutrient additions in plots located at 2000m above sea level. Roots were extracted and intraradical AMF abundance determined microscopically; the AMF community was analyzed by 454-pyrosequencing targeting the large subunit rDNA. We identified 74 operational taxonomic units (OTUs) with a large proportion of Diversisporales. N additions provoked a significant decrease in intraradical abundance, whereas AMF richness was reduced significantly by N and P additions, with the strongest effect in the combined treatment (39% fewer OTUs), mainly influencing rare species. We identified a differential effect on phylogenetic groups, with Diversisporales richness mainly reduced by N additions in contrast to Glomerales highly significantly affected solely by P. Regarding AMF community structure we observed a compositional shift when analyzing presence/absence data following P additions. In conclusion, N and P additions in this ecosystem affect AMF abundance, but especially AMF species richness; these changes might influence plant community composition and productivity and by that various ecosystem processes. This article is protected by copyright. All rights reserved.

Description: With the rapidly expanding ecological footprint of agriculture, the design of farmed landscapes will play an increasingly important role for both carbon storage and biodiversity protection. Carbon and biodiversity can be enhanced by integrating natural habitats into agricultural lands, but a key question is whether benefits are maximized by including many small features throughout the landscape (‘land-sharing’ agriculture) or a few large contiguous blocks alongside intensive farmland (‘land-sparing’ agriculture). In this study, we are the first to integrate carbon storage alongside multi-taxa biodiversity assessments to compare land-sparing and land-sharing frameworks. We do so by sampling carbon stocks and biodiversity (birds and dung beetles) in landscapes containing agriculture and forest within the Colombian Chocó-Andes, a zone of high global conservation priority. We show that woodland fragments embedded within a matrix of cattle pasture hold less carbon per unit area than contiguous primary or advanced secondary forests (〉15 years). Farmland sites also support less diverse bird and dung beetle communities than contiguous forests, even when farmland retains high levels of woodland habitat cover. Landscape simulations based on these data suggest that land-sparing strategies would be more beneficial for both carbon storage and biodiversity than land-sharing strategies across a range of production levels. Biodiversity benefits of land-sparing are predicted to be similar whether spared lands protect primary or advanced secondary forests, owing to the close similarity of bird and dung beetle communities between the two forest classes. Land-sparing schemes that encourage the protection and regeneration of natural forest blocks thus provide a synergy between carbon and biodiversity conservation, and represent a promising strategy for reducing the negative impacts of agriculture on tropical ecosystems. However, further studies examining a wider range of ecosystem services will be necessary to fully understand the links between land-allocation strategies and long-term ecosystem service provision.

Description: We have developed a technique for estimating the temporal evolution of the plasmaspheric helium ion density based on a sequence of extreme ultraviolet (EUV) data obtained from the IMAGE satellite. In the proposed technique, the estimation is obtained by incorporating EUV images from IMAGE into a two-dimensional fluid model of the plasmasphere using a data assimilation approach based on the ensemble transform Kalman filter. Since the motion and the spatial structure of the helium plasmasphere is strongly controlled by the electric field in the inner magnetosphere, the electric field around the plasmapause can also be estimated using the ensemble transform Kalman filter. We performed an experiment using synthetic images that were generated from the same numerical model under a certain condition. It was confirmed that the condition that generated the synthetic images was successfully reproduced. We also present some results obtained using real EUV imaging data. Finally, we discuss the possibility of estimating the density profile along a magnetic field line. Since each EUV image was taken from a different direction due to the motion of the IMAGE satellite, we could obtain the information on the density profile along a field line by combining multiple images.

Description: Small-scale structure of the plasma convection and electron content within the subauroral polarization stream (SAPS) is investigated. We present ionospheric observations during the main phase of the geomagnetic storm on March 17, 2013, during which a sequence of intense, highly localized, and fast-moving electric field (EF) structures within SAPS was observed by the SuperDARN Christmas Valley West radar (CVW). The CVW EF measurements at 60-s resolution are analyzed in context of coincident GPS measurements of the total electron content (TEC) at 30-s resolution. The strong and narrow feature of the subauroral ion drift (SAID) was observed poleward of the TEC trough, with a TEC enhancement (peak) seen in the SAPS (SAID) region. The SAPS wave activity commenced ~2 hours (15 min) after first appearance of SAPS (SAID). The SAPS structures appeared near the poleward edge of the trough, propagated westward, and merged with SAID near TEC peak. The propagation velocity was comparable with convection velocity within each EF structure. The SAPS TEC exhibited a general decrease towards the end of the period. On a smaller time scale, TEC exhibited a small but appreciable decrease within EF structures. The wavelet spectra of EF and TEC showed similar variations, with wave period of ~5-min period near onset and increasing to 8–10 min towards the end of the period with significant wave activity. A scenario is discussed, in which the SAPS wave activity may modify the ionospheric conductance and TEC at small scales, with large-scale magnetosphere-ionosphere feedback acting to continuously deplete TEC where/when such activity does not occur.

Description: The intense inner radiation belt at Jupiter (〉50 MeV at 1.5 R J ) is generally accepted to be created by radial diffusion of electrons from further away from the planet. However, this requires a source with energies that exceed1 MeV outside the orbit of the moon Io at 5.9 R J , which has never been explained satisfactorily. Here we test the hypothesis that this source population could be formed from a very soft energy spectrum, by particle injection processes and resonant electron acceleration via whistler mode chorus waves. We use the BAS Radiation Belt Model to calculate the change in the electron flux between 6.5 and 15 R J ; these are the first simulations at Jupiter combining wave particle interactions and radial diffusion. The resulting electron flux at 100 keV and 1 MeV lies very close to the Galileo Interim Radiation Electron model spectrum after 1 and 10 days respectively. The primary driver for the increase in the flux is cyclotron resonant acceleration by chorus waves. A peak in phase space density forms such that inside L ≈ 9 radial diffusion transports electrons towards Jupiter, but outside L ≈ 9 radial diffusion acts away from the planet. The results are insensitiveto the softness of the initial energy spectrum but do depend on the value of the flux at the minimum energy boundary. We conclude by suggesting that the source population for the inner radiation belt at Jupiter could indeed be formed by wave-particle interactions.

Description: Enceladus’ southern plume is one of the major discoveries of the Cassini mission. The water neutrals and ice crystals ejected by the cryovolcanic activity populate Saturn's E-ring and the neutral torus, and they interact with the plasma environment of Saturn's magnetosphere. The plasma neutrality inside Enceladus’ plume has been shown by the Langmuir probe measurement to be modified by the presence of the dust particles. We present an independent method of determining the electron density inside the plume. Sometimes after dust impacts, plasma oscillations (ringing) were detected by the Cassini Radio and Plasma Wave Science (RPWS) instrument. The frequencies of these oscillations have been shown to be consistent with the local plasma frequency, thus providing a measurement of the local electron density.

Description: The study of complexity in two aspects of the magnetic activity in the Sun-Earth system is presented. We compare the temporal evolution of the magnetic fluctuations in the Earth's magnetosphere, and the spatial distribution of the magnetic field in the solar photosphere, by calculating fractal dimensions from the data. It is found that the fractal dimension of the D st data decreases during magnetic storm states, and is well correlated with other indexes of solar activity, such as the solar flare and coronal indexes. This correlation holds for individual storms, full year data, and the complete 23rd solar cycle. The fractal dimension from solar magnetogram data also correlates well with both the D st index and solar flare index, although the correlation is much more clear at the larger temporal scale of the 23rd solar cycle, showing a clear increase around solar maximum.