ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (8)
  • Wiley  (8)
  • American Association for the Advancement of Science (AAAS)
  • Journal of Geophysical Research JGR - Space Physics  (5)
  • Journal of Geophysical Research: Space Physics  (3)
  • 7531
  • Physics  (8)
  • 1
    facet.materialart.
    Unknown
    Statistical study of ELF/VLF emissions at subauroral latitudes in Athabasca, Canada (2015)
    Wiley
    Details
    Publication Date: 2015-09-11
    Description: We present the first statistical analysis of ELF/VLF emissions observed on the ground at subauroral latitudes that includes their features, occurrences and association with solar wind and geomagnetic variations. Using a 100 kHz sampling loop antenna located in Athabasca, Canada (54.60 ∘ N, 246.36 ∘ E, L=4.3) we monitored these emissions, including chorus, quasi-periodic emissions, and hiss, from November 2012 to October 2013. We found a maximum occurrence rate in the morning sector (06–07 MLT) and a minimum in the night sector (∼18 to 02 MLT), in agreement with previous satellite measurements in the inner magnetosphere. We also found correlation between the ongoing substorm and storm activity and the increase of occurrence rates. The observed waves usually had a central frequency ∼1–3 kHz lower than the half gyro-frequency at the conjugate equatorial plane, indicating a wave source at higher latitudes. A superposed epoch analysis showed that the starting time of the ELF/VLF emissions is preceded by a rise in AE both on short (hours) and long (days) terms. Solar wind speed also started slowly rising ∼1.5 days before, while density and dynamic pressure decreased shortly afterwards. This may signify that high-speed solar wind conditions also contribute to the generation of ELF/VLF emissions detected at subauroral latitudes.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    Conjugate observations of dayside and nightside VLF chorus and QP emissions between Arase (ERG) and Kannuslehto, Finland (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract We compare for the first time two conjugate events showing simultaneous VLF wave observations between the same ground‐station and spacecraft, at different geomagnetic conditions and on opposite sides of the magnetosphere. Waves were observed at Kannuslehto [MLAT=64.4N, L=5.46], Finland, and Arase (ERG) in the inner magnetosphere. Case 1 on 28 March 2017, shows quasi‐periodic (QP) emissions and chorus simultaneously observed on the post‐midnight side during the recovery phase of a storm, with sustained high solar‐wind speed and AE index. Case 2 on 30 November 2017 shows clear one‐to‐one correspondence of QP elements on the noon side during geomagnetic quiet time (Dst 〉 10 nT and AE 〈 100 nT). We present the characteristics of both cases, focusing on coherence and spatial extent of the waves, electron density and magnetic field variations. We report that the magnetic field gradient plays a role in the changes of spectral features of the waves.
    Print ISSN: 2169-9380
    Electronic ISSN: 2169-9402
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Determination of the Signal Fluctuation Threshold of the Temperature‐Ion Composition Ambiguity Problem Using Monte Carlo Simulations (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Unambiguously estimating the plasma parameters of the ionosphere at altitudes between 130 and 300 km presents a problem for the Incoherent Scatter Radar (ISR). At these ranges, ISR is unable to distinguish between different mixtures of molecular ions (NO+ and O2+) and atomic oxygen ions (O+). Common solutions to this problem are either to employ empirical or theoretical models of the ionosphere, or to add a priori known plasma parameter information obtained from the Plasma Line of the ISR spectrum. Studies have demonstrated that plasma parameters can be unambiguously estimated in almost noiseless scenarios, not commonly feasible during routine monitoring. In this study, we define a theoretical framework to quantify the ambiguity problem and determine the maximum signal fluctuation levels of the ISR signal to unambiguously estimate plasma parameters. We conduct Monte Carlo simulations for different plasma parameters to evaluate the estimation performance of the most commonly used Non‐Linear Least Squares optimization algorithm. Results are shown as probability curves of valid convergence and ‘correct’ estimation. We use simulations to quantify the estimation error when using ionospheric models as initial conditions of the optimization algorithm. We also determine the contribution to the estimation process of different combinations of parameters known from the Plasma Line, the particular contribution of each plasma parameter, and the effect of increasing the level of uncertainty of the parameters known a priori. Results suggest that knowing a priori both electron density and electron temperature parameters allows an unambiguous estimation even at high fluctuation levels.
    Print ISSN: 2169-9380
    Electronic ISSN: 2169-9402
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    ELF/VLF wave propagation at subauroral latitudes: Conjugate observation between the ground and Van Allen Probes A (2016)
    Wiley
    Details
    Publication Date: 2016-06-03
    Description: We report simultaneous observation of ELF/VLF emissions, showing similar spectral and frequency features, between a VLF receiver at Athabasca (ATH), Canada (L=4.3) and Van Allen Probes A (RBSP A). Using a statistical database from November 1, 2012 to October 31, 2013, we compared a total of 347 emissions observed on the ground with observations made by RBSP in the magnetosphere. On 25 February 2013, from 12:46 to 13:39 UT in the dawn sector (04-06 MLT), we observed a quasi-periodic (QP) emission centered at 4 kHz, and an accompanying short pulse lasting less than a second at 4.8 kHz in the dawn sector (04-06 MLT). RBSP-A wave data showed both emissions as right-hand polarized with their Poynting vector earthward to the northern hemisphere. Using cross-correlation analysis, we did, for the first time, time delay analysis of a conjugate ELF/VLF event between ground and space, finding  +2 to +4 s (ATH first) for the QP and  -3 s (RBSP-A first) for the pulse. Using backwards tracing from ATH to the geomagnetic equator and forward tracing from the equator to RBSP-A, based on plasmaspheric density observed by the spacecraft, we validate a possible propagation path for the QP emission which is consistent with the observed time delay.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    Space charge effects and arc properties of simulated lightning on Venus (2011)
    Wiley
    Details
    Publication Date: 2011-06-19
    Description: An experimental investigation of the physical properties of lightning on Venus was carried out by applying fast impulses to a pressurized (1–2.8 atm) CO2-N2 gas mix. The maximum current employed in the experiments was 2.8 kA. It was found that the pressure has a marked effect on the measured electric field. This effect is mostly due to negative ions created by electron attachment. This negative space charge could hamper breakdown on Venus if the clouds are negatively charged. Using a time-resolved spectroscopic technique, the instantaneous temperature of the arc was measured. This varies from 29,000 K soon after the arc appears to 14,000 K some 15 μs later. The arc's linear resistance and the power it dissipates were estimated using the Spitzer resistivity model and the measured temperatures. The linear resistance was found to be in the 17–233 Ω m−1 interval, which is comparable to the values of terrestrial lightning. The by-products of the discharge were analyzed using a mass analyzer, and it was found that the discharge decomposes the CO2 into CO and O at similar rates. Our estimate of the CO yield is 2.7 × 1018 molecules J−1.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 6
    facet.materialart.
    Unknown
    Variability of Precipitating Ion Fluxes During the September 2017 Event at Mars (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract In this work, we study the influence of the September 2017 solar event on the precipitating heavy ion fluxes toward Mars' atmosphere as seen by Mars Atmosphere and Volatile EvolutioN/Solar Wind Ion Analyzer, an energy and angular ion spectrometer and by Mars Atmosphere and Volatile EvolutioN/Suprathermal and Thermal Ion Composition instrument, an energy, mass, and angular ion spectrometer. After a careful reconstruction of the background induced by the Solar Energetic Particle event in the Mars Atmosphere and Volatile EvolutioN/Solar Wind Ion Analyzer spectrometer, we investigate the precipitating ion flux responses to the space weather events that took place in September 2017. This period is a unique opportunity to analyze the respective role of various possible drivers of heavy ion precipitation into Mars' atmosphere with a wide range of different space weather events occurring during the same month. This study shows an increase in the precipitation flux by more than 1 order of magnitude during the arrival of the September Interplanetary Coronal Mass Ejection compared to the average flux during quiet solar conditions. We also showed that among the possible solar drivers, the solar wind dynamic pressure is the most significant during September 2017.
    Print ISSN: 2169-9380
    Electronic ISSN: 2169-9402
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 7
    facet.materialart.
    Unknown
    The Solar Probe Plus Radio Frequency Spectrometer: Measurement Requirements, Analog Design, and Digital Signal Processing (2017)
    Wiley
    Details
    Publication Date: 2017-03-04
    Description: The Radio Frequency Spectrometer (RFS) is a two channel digital receiver and spectrometer, which will make remote sensing observations of radio waves and in situ measurements of electrostatic and electromagnetic fluctuations in the solar wind. A part of the FIELDS suite for Solar Probe Plus (SPP), the RFS is optimized for measurements in the inner heliosphere, where solar radio bursts are more intense and the plasma frequency is higher compared to previous measurements at distances of 1 AU or greater. The inputs to the RFS receiver are the four electric antennas mounted near the front of the SPP spacecraft, and a single axis of the SPP search coil magnetometer (SCM). Each RFS channel selects a monopole or dipole antenna input, or the SCM input, via multiplexers. The primary data products from the RFS are auto and cross spectra from the selected inputs. The spectra are calculated using a polyphase filter bank (PFB), which enables the measurement of low amplitude signals of interest in the presence of high amplitude narrowband noise generated by spacecraft systems. We discuss the science signals of interest driving the RFS measurement objectives, describe the RFS analog design and digital signal processing, and show examples of current performance.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 8
    facet.materialart.
    Unknown
    Comparison between low-pressure laboratory discharges and atmospheric sprites (2016)
    Wiley
    Details
    Publication Date: 2016-12-30
    Description: The discharge of a charged dielectric in low pressure air has characteristics that resemble some of the features of mesospheric discharges. The dielectric discharges in steps when the pressure of the surrounding air is gradually reduced from nearly atmospheric to ~0.01 torr. The set-up employed here decouples the discharge from the power supply and, thanks to that, unique properties of the discharge manifest themselves. For example: in the pressure interval ~10-100 torr streamers are emitted from the surface of the dielectric but when the pressure decreases to 2-16 torr these are replaced by spherically symmetrical discharges that we call peonies. These have interesting properties, like: a) they do not produce electrical field, b) they remain static and c) their size increases with decreasing pressure. The peonies are a type of discharge that has not been reported before. They resemble sprite beads and are assumed to consist of large avalanches that do not lead to the formation of a streamer. At further lower pressures, in the interval 0.01-0.1 torr, diffuse volume discharges were observed that have some morphological similarities with sprite halos and the top of columnar sprites. The spectrographic measurements carried out show that the discharges have bands from the first and second positive system in N 2 as well as lines of N 2 + . Quenching of the first negative system of N 2 was observed at 3 torr. In this work it was also observed how a cosmic ray can go on to trigger a discharge inside the experimentation chamber.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...