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  • Articles  (40)
  • Wiley  (40)
  • American Chemical Society
  • American Institute of Physics (AIP)
  • National Academy of Sciences
  • Nature Publishing Group
  • Springer Nature
  • Space Weather  (21)
  • Journal of Geophysical Research JGR - Atmospheres  (19)
  • 39520
  • 7528
  • 1
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    A major solar eruptive event in July 2012: Defining extreme space weather scenarios (2013)
    Wiley
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    Publication Date: 2013-09-20
    Description: [1]  A key goal for space weather studies is to define severe and extreme conditions that might plausibly afflict human technology. On 23 July 2012 solar active region 1520 (~141°W heliographic longitude) gave rise to a powerful coronal mass ejection (CME) with an initial speed that was determined to be 2500±500 km/s. The eruption was directed away from Earth toward 125°W longitude. STEREO-A sensors detected the CME arrival only about 19 hours later and made in situ measurements of the solar wind and interplanetary magnetic field. In this paper we address the question of what would have happened if this powerful interplanetary event had been Earthward directed. Using a well-proven geomagnetic storm forecast model, we find that the 23-24 July event would certainly have produced a geomagnetic storm that was comparable to the largest events of the 20th Century (Dst ~ -500nT). Using plausible assumptions about seasonal and time-of-day orientation of the Earth's magnetic dipole, the most extreme modeled value of storm-time disturbance would have been Dst = -1182nT. This is considerably larger than estimates for the famous Carrington storm of 1859. This finding has far reaching implications because it demonstrates that extreme space weather conditions such as those during March of 1989 or September of 1859 can happen even during a modest solar activity cycle such as the one presently underway. We argue that this extreme event should immediately be employed by the space weather community to model severe space weather effects on technological systems such as the electric power grid.
    Print ISSN: 1539-4964
    Electronic ISSN: 1542-7390
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    An inter-comparison of inverse models for estimating sources and sinks of CO2 using GOSAT measurements (2015)
    Wiley
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    Publication Date: 2015-05-08
    Description: This study presents the outcome of an inverse modeling inter-comparison experiment on the use of total column CO 2 retrievals from GOSAT for quantifying global sources and sinks of CO 2 . Eight research groups submitted inverse modeling results for the first year of GOSAT measurements. Inversions were carried out using only GOSAT data, a combination of GOSAT and surface measurements, and using only surface measurements. As expected, the most robust flux estimates are obtained at large scales (e.g. within 20% of the annual flux at the global scale), and they quickly diverge towards the scale of the sub-continental TRANSCOM regions and beyond (to〉100% of the annual flux). We focus our analysis on a shift in the CO 2 uptake over land from the Tropics towards the Northern Hemisphere Extra tropics of ~1 PgC/yr when GOSAT data are used in the inversions. This shift is largely driven by TRANSCOM regions Europe and Northern Africa, showing, respectively, an increased uptake and release of 0.7 and 0.9 PgC/yr. Inversions using GOSAT data show a reduced gradient between mid latitudes of the Northern Hemisphere and the Tropics, consistent with the latitudinal shift in carbon uptake. However, the reduced gradients degrade the agreement with background aircraft and surface measurements. To narrow the range of inversion-derived flux estimates will require further efforts to understand the differences not only between the retrieval schemes but also between inverse models, as their contributions to the overall uncertainty are estimated to be of similar magnitude.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 3
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    A Study of SuperDARN Response to Co‐occurring Space Weather Phenomena (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract The Sun was remarkably active during the first week of September 2017 producing numerous solar flares, solar radiation storms and coronal mass ejections (CME). This activity caused disruption to terrestrial high frequency (HF, 3‐30 MHz) radio communication channels including observations with the SuperDARN HF radars. In this paper, we analyze the response of SuperDARN ground‐scatter observations and decreases in background sky noise level in response to multiple solar flares occurring in quick succession and co‐occurring with solar energetic protons and auroral activity. We estimate the attenuation in HF signal strength using an approach similar to riometry and find that the radars exhibit a nonlinear response to compound solar flare events. Additionally, we find the three different space weather drivers have varying degrees of influence on the HF signal properties at different latitudes. Our study demonstrates that in addition to monitoring high latitude convection, SuperDARN observations can be used to study the spatiotemporal evolution of disruption to HF communication during extreme space weather conditions.
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    Topics: Geosciences , Physics
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  • 4
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    “Resource Letter” for Space Weather (2016)
    Wiley
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    Publication Date: 2016-08-20
    Description: Key Points Resource Letter for space weather Reference to article with extensive referecnes
    Print ISSN: 1539-4964
    Electronic ISSN: 1542-7390
    Topics: Geosciences , Physics
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  • 5
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    Seasonality of westerly moisture transport in the East Asian Summer Monsoon and its implications for interpreting precipitation δ18O (2015)
    Wiley
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    Publication Date: 2015-05-26
    Description: East Asian Summer Monsoon (EASM) rainfall impacts the world's most populous regions. Accurate EASM rainfall prediction necessitates robust palaeoclimate reconstructions from proxy data and quantitative linkage to modern climatic conditions. Many precisely-dated oxygen isotope records from Chinese stalagmites have been interpreted as directly reflecting past EASM rainfall amount variability, but recent research suggests such records instead integrate multiple hydroclimatic processes. Using a Lagrangian precipitation moisture source diagnostic, we demonstrate that EASM rainfall is primarily derived from the Indian Ocean. Conversely, Pacific Ocean moisture export peaks during winter and the moisture uptake area does not differ significantly between summer and winter, and is thus a minor contributor to monsoonal precipitation. Our results are substantiated by an accurate reproduction of summer and winter spatial rainfall distributions across China. We also correlate modern EASM rainfall oxygen isotope ratios with instrumental rainfall amount and our moisture source data. This analysis reveals that the strength of the source effect is geographically variable, and differences in atmospheric moisture transport may significantly impact the isotopic signature of EASM rainfall at the Hulu, Dongge and Wanxiang Cave sites. These results improve our ability to isolate the rainfall amount signal in palaeomonsoon reconstructions and indicate that precipitation across central and eastern China will directly respond to variability in Indian Ocean moisture supply.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 6
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    The Role of Universities in a Vigorous National Space Weather Program (2011)
    Wiley
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    Publication Date: 2011-05-05
    Description: It is increasingly clear that U.S. economic vitality and development, as well as global competitiveness, have strong and enduring ties to the space segment. Remote sensing, communications, surveillance, and a host of other areas of U.S. leadership are underpinned by space technology. Moreover, our national pursuit of robotic and human space exploration remains a cornerstone of U.S. aspirations. As was made clear in the U.S. National Space Policy (NSP) issued by President Barack Obama on 28 June 2010, a central overlay of the U.S. space program is that we must understand, be able to forecast, and, if possible, mitigate the effects of the space environment on technological systems.
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    Topics: Geosciences , Physics
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  • 7
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    Distribution of methane in the tropical upper troposphere measured by CARIBIC and CONTRAIL aircraft (2012)
    Wiley
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    Publication Date: 2012-10-04
    Description: We investigate the upper tropospheric distribution of methane (CH4) at low latitudes based on the analysis of air samples collected from aboard passenger aircraft. The distribution of CH4 exhibits spatial and seasonal differences, such as the pronounced seasonal cycles over tropical Asia and elevated mixing ratios over central Africa. Over Africa, the correlations of methane, ethane, and acetylene with carbon monoxide indicate that these high mixing ratios originate from biomass burning as well as from biogenic sources. Upper tropospheric mixing ratios of CH4 were modeled using a chemistry transport model. The simulation captures the large-scale features of the distributions along different flight routes, but discrepancies occur in some regions. Over Africa, where emissions are not well constrained, the model predicts a too steep interhemispheric gradient. During summer, efficient convective vertical transport and enhanced emissions give rise to a large-scale CH4 maximum in the upper troposphere over subtropical Asia. This seasonal (monsoonal) cycle is analyzed with a tagged tracer simulation. The model confirms that in this region convection links upper tropospheric mixing ratios to regional sources on the Indian subcontinent, subtropical East Asia, and Southeast Asia. This type of aircraft data can therefore provide information about surface fluxes.
    Print ISSN: 0148-0227
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  • 8
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    The Third Electric Infrastructure Security World Summit Meeting (2012)
    Wiley
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    Publication Date: 2012-07-12
    Description: Almost 150 scientists, engineers, policy makers, and industry leaders from more than 20 countries met at the Electric Infrastructure Security (EIS) summit meeting in London to iron out recommendations on how to potentially protect power grid infrastructure in the event of an extreme space weather event.
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  • 9
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    Science for a Technological Society: The 2013–2022 Decadal Survey in Solar and Space Physics (2013)
    Wiley
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    Publication Date: 2013-02-17
    Print ISSN: 1539-4964
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    Topics: Geosciences , Physics
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  • 10
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    The Global Positioning System constellation as a space weather monitor: Comparison of electron measurements with Van Allen Probes data (2016)
    Wiley
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    Publication Date: 2016-01-27
    Description: Energetic electron observations in Earth's radiation belts are typically sparse and multi-point studies often rely on serendipitous conjunctions. This paper establishes the scientific utility of the Combined X-ray Dosimeter (CXD), currently flown on 19 satellites in the Global Positioning System (GPS) constellation, by cross-calibrating energetic electron measurements against data from the Van Allen Probes. By breaking our cross-calibration into two parts – one that removes any spectral assumptions from the CXD flux calculation, and one that compares the energy spectra – we first validate the modeled instrument response functions, then the calculated electron fluxes. Unlike previous forward modeling of energetic electron spectra we use a combination of four distributions that, together, capture a wide range of observed spectral shapes. Our two-step approach allowed us to identify, and correct for, small systematic offsets between block IIR and IIF satellites. Using the Magnetic Electron Ion Spectrometer (MagEIS) and Relativistic Electron-Proton Telescope (REPT) on Van Allen Probes as a “gold standard” we demonstrate that the CXD instruments are well-understood. A robust statistical analysis shows that CXD and Van Allen Probes fluxes are similar and the measured fluxes from CXD are typically within a factor of 2 of Van Allen Probes at energies ≲4 MeV. We present data from 17 CXD-equipped GPS satellites covering the 2015 “St. Patrick's Day” geomagnetic storm to illustrate the scientific applications of such a high data density satellite constellation, and therefore demonstrate that the GPS constellation is positioned to enable new insights in inner magnetospheric physics and space weather forecasting.
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