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Found 879 results
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Authors: Bin Kang Suk-, Fok Mei-Ching, Komar Colin, Glocer Alex, Li Wen, et al.
Title: An energetic electron flux dropout due to magnetopause shadowing on 1 June 2013
Abstract: We examine the mechanisms responsible for the dropout of energetic electron flux during 31 May – 1 June 2013, using Van Allen Probe (RBSP) electron flux data and simulations with the Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. During storm main phase, L-shells at RBSP locations are greater than ~ 8, which are connected to open drift shells. Consequently, diminished electron fluxes were observed over a wide range of energies. The combination of drift shell splitting, magnetopause shadowing and drift loss all result in butterfly electron pitch-angle distributions (PADs) at the nightside. During storm sudden commencement, RBSP observations display electron butterfly PADs over a wide range of energies. However, it is difficult to determine whether there are butterfly PADs duri. . .
Date: 01/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024879 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024879/full
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Authors: Turner D. L., Claudepierre S G, Fennell J. F., O'Brien T P, Blake J B, et al.
Title: Energetic electron injections deep into the inner magnetosphere associated with substorm activity
Abstract: From a survey of the first nightside season of NASA's Van Allen Probes mission (Dec/2012 – Sep/2013), 47 energetic (10s to 100s of keV) electron injection events were found at L-shells ≤ 4, all of which are deeper than any previously reported substorm-related injections. Preliminary details from these events are presented, including how: all occurred shortly after dipolarization signatures and injections were observed at higher L-shells; the deepest observed injection was at L~2.5; and, surprisingly, L≤4 injections are limited in energy to ≤250 keV. We present a detailed case study of one example event revealing that the injection of electrons down to L~3.5 was different from injections observed at higher L and likely resulted from drift resonance with a fast magnetosonic wave in t. . .
Date: 02/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL063225 Available at: http://doi.wiley.com/10.1002/2015GL063225
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Authors: Lejosne ène, Kunduri B. S. R., Mozer F S, and Turner D. L.
Title: Energetic electron injections deep into the inner magnetosphere: a result of the subauroral polarization stream (SAPS) potential drop
Abstract: It has been reported that the dynamics of energetic (tens to hundreds of keV) electrons and ions is inconsistent with the theoretical picture in which the large‐scale electric field is a superposition of corotation and convection electric fields. Combining one year of measurements by the Super Dual Auroral Radar Network, DMSP F‐18 and the Van Allen Probes, we show that subauroral polarization streams are observed when energetic electrons have penetrated below L = 4. Outside the plasmasphere in the premidnight region, potential energy is subtracted from the total energy of ions and added to the total energy of electrons during SAPS onset. This potential energy is converted into radial motion as the energetic particles drift around Earth and leave the SAPS azimuthal sector. As a result, . . .
Date: 04/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL077969 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL077969
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Authors: Oyama S., Kero A., Rodger C. J., Clilverd M A, Miyoshi Y, et al.
Title: Energetic electron precipitation and auroral morphology at the substorm recovery phase
Abstract: It is well known that auroral patterns at the substorm recovery phase are characterized by diffuse or patch structures with intensity pulsation. According to satellite measurements and simulation studies, the precipitating electrons associated with these aurorae can reach or exceed energies of a few hundreds of keV through resonant wave-particle interactions in the magnetosphere. However, because of difficulty of simultaneous measurements, the dependency of energetic electron precipitation (EEP) on auroral morphological changes in the mesoscale has not been investigated to date. In order to study this dependency, we have analyzed data from the European Incoherent Scatter (EISCAT) radar, the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) riometer, collocated cameras, ground-based m. . .
Date: 05/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023484 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023484/full
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Authors: Miyoshi Y, Oyama S., Saito S., Kurita S., Fujiwara H., et al.
Title: Energetic electron precipitation associated with pulsating aurora: EISCAT and Van Allen Probe observations
Abstract: Pulsating auroras show quasi-periodic intensity modulations caused by the precipitation of energetic electrons of the order of tens of keV. It is expected theoretically that not only these electrons but also sub-relativistic/relativistic electrons precipitate simultaneously into the ionosphere owing to whistler-mode wave–particle interactions. The height-resolved electron density profile was observed with the European Incoherent Scatter (EISCAT) Tromsø VHF radar on 17 November 2012. Electron density enhancements were clearly identified at altitudes >68 km in association with the pulsating aurora, suggesting precipitation of electrons with a broadband energy range from ~10 keV up to at least 200 keV. The riometer and network of subionospheric radio wave observations also showed the energ. . .
Date: 03/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020690 Available at: http://doi.wiley.com/10.1002/2014JA020690
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Authors: Capannolo L., Li W, Ma Q, Shen X.‐C., Zhang X.‐J., et al.
Title: Energetic Electron Precipitation: Multievent Analysis of Its Spatial Extent During EMIC Wave Activity
Abstract: Electromagnetic ion cyclotron (EMIC) waves can drive precipitation of tens of keV protons and relativistic electrons, and are a potential candidate for causing radiation belt flux dropouts. In this study, we quantitatively analyze three cases of EMIC‐driven precipitation, which occurred near the dusk sector observed by multiple Low‐Earth‐Orbiting (LEO) Polar Operational Environmental Satellites/Meteorological Operational satellite programme (POES/MetOp) satellites. During EMIC wave activity, the proton precipitation occurred from few tens of keV up to hundreds of keV, while the electron precipitation was mainly at relativistic energies. We compare observations of electron precipitation with calculations using quasi‐linear theory. For all cases, we consider the effects of other magn. . .
Date: 03/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026291 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026291
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Authors: Meredith Nigel P, Horne Richard B, Glauert Sarah A, Thorne Richard M, Summers D., et al.
Title: Energetic outer zone electron loss timescales during low geomagnetic activity
Abstract: Following enhanced magnetic activity the fluxes of energetic electrons in the Earth's outer radiation belt gradually decay to quiet-time levels. We use CRRES observations to estimate the energetic electron loss timescales and to identify the principal loss mechanisms. Gradual loss of energetic electrons in the region 3.0 ≤ L ≤ 5.0 occurs during quiet periods (Kp < 3−) following enhanced magnetic activity on timescales ranging from 1.5 to 3.5 days for 214 keV electrons to 5.5 to 6.5 days for 1.09 MeV electrons. The intervals of decay are associated with large average values of the ratio fpe/fce (>7), indicating that the decay takes place in the plasmasphere. We compute loss timescales for pitch-angle scattering by plasmaspheric hiss using the PADIE code with wave properties based on C. . .
Date: 05/2006 Publisher: Journal of Geophysical Research DOI: 10.1029/2005JA011516 Available at: http://onlinelibrary.wiley.com/doi/10.1029/2005JA011516/abstract
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Authors: Mauk B H, Blake J B, Baker D N, Clemmons J. H., Reeves G D, et al.
Title: The Energetic Particle Detector (EPD) Investigation and the Energetic Ion Spectrometer (EIS) for the Magnetospheric Multiscale (MMS) Mission
Abstract: The Energetic Particle Detector (EPD) Investigation is one of 5 fields-and-particles investigations on the Magnetospheric Multiscale (MMS) mission. MMS comprises 4 spacecraft flying in close formation in highly elliptical, near-Earth-equatorial orbits targeting understanding of the fundamental physics of the important physical process called magnetic reconnection using Earth’s magnetosphere as a plasma laboratory. EPD comprises two sensor types, the Energetic Ion Spectrometer (EIS) with one instrument on each of the 4 spacecraft, and the Fly’s Eye Energetic Particle Spectrometer (FEEPS) with 2 instruments on each of the 4 spacecraft. EIS measures energetic ion energy, angle and elemental compositional distributions from a required low energy limit of 20 keV for protons and 45 keV for o. . .
Date: 06/2014 Publisher: Space Science Reviews DOI: 10.1007/s11214-014-0055-5 Available at: http://link.springer.com/10.1007/s11214-014-0055-5http://link.springer.com/content/pdf/10.1007/s11214-014-0055-5
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Authors: Summers Danny, Shi Run, Engebretson Mark J, Oksavik Kjellmar, Manweiler Jerry W., et al.
Title: Energetic proton spectra measured by the Van Allen Probes
Abstract: We test the hypothesis that pitch-angle scattering by electromagnetic ion cyclotron (EMIC) waves can limit ring current proton fluxes. For two chosen magnetic storms, during March 17-20, 2013 and March 17-20, 2015, we measure proton energy spectra in the region 3 ≤ L ≤ 6 using the RBSPICE B instrument on the Van Allen Probes. The most intense proton spectra are observed to occur during the recovery periods of the respective storms. Using proton precipitation data from the POES (NOAA and MetOp) spacecraft, we deduce that EMIC wave action was prevalent at the times and L-shell locations of the most intense proton spectra. We calculate limiting ring current proton energy spectra from recently developed theory. Comparisons between the observed proton energy spectra and the theoreti. . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024484 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024484/full
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Authors: Brito T, Woodger L, Hudson M K, and MILLAN R
Title: Energetic radiation belt electron precipitation showing ULF modulation
Abstract: 1] The energization and loss processes for energetic radiation belt electrons are not yet well understood. Ultra Low Frequency (ULF) waves have been correlated with both enhancement in outer zone radiation belt electron flux and modulation of precipitation loss to the atmosphere. This study considers the effects of ULF waves in the Pc-4 to Pc-5 period range (45 s–600 s) on electron loss to the atmosphere on a time scale of several minutes. Global simulations using magnetohydrodynamics (MHD) model fields as drivers provide a valuable tool for studying the dynamics of these ∼MeV energetic particles. ACE satellite measurements of the MHD solar wind parameters are used as the upstream boundary condition for the Lyon-Fedder-Mobarry (LFM) 3D MHD code calculation of fields, used to drive elec. . .
Date: 11/2012 Publisher: Geophysical Research Letters Pages: 28 DOI: 10.1029/2012GL053790 Available at: http://onlinelibrary.wiley.com/doi/10.1029/2012GL053790/full
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Authors: Drozdov A. Y., Shprits Y Y, Orlova K.G., Kellerman A. C., Subbotin D. A., et al.
Title: Energetic, relativistic and ultra-relativistic electrons: Comparison of long-term VERB code simulations with Van Allen Probes measurements
Abstract: In this study, we compare long-term simulations performed by the Versatile Electron Radiation Belt (VERB) code with observations from the MagEIS and REPT instruments on the Van Allen Probes satellites. The model takes into account radial, energy, pitch-angle and mixed diffusion, losses into the atmosphere, and magnetopause shadowing. We consider the energetic (>100 keV), relativistic (~0.5-1 MeV) and ultra-relativistic (>2 MeV) electrons. One year of relativistic electron measurements (μ=700 MeV/G) from October 1, 2012 to October 1, 2013, are well reproduced by the simulation during varying levels of geomagnetic activity. However, for ultra-relativistic energies (μ=3500 MeV/G), the VERB code simulation overestimates electron fluxes and Phase Space Density. These results indicate that an . . .
Date: 04/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020637 Available at: http://doi.wiley.com/10.1002/2014JA020637
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Authors: Sandhu J. K., Rae I. J., Freeman M. P., Forsyth C., Gkioulidou M., et al.
Title: Energisation of the ring current by substorms
Abstract: The substorm process releases large amounts of energy into the magnetospheric system, although where the energy is transferred to and how it is partitioned remains an open question. In this study, we address whether the substorm process contributes a significant amount of energy to the ring current. The ring current is a highly variable region, and understanding the energisation processes provides valuable insight into how substorm ‐ ring current coupling may contribute to the generation of storm conditions and provide a source of energy for wave driving. In order to quantify the energy input into the ring current during the substorm process, we analyse RBSPICE and HOPE ion flux measurements for H+, O+, and He+. The energy content of the ring current is estimated and binned spatially for. . .
Date: 09/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025766 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025766
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Authors: Chen Yue, Reeves Geoffrey D, and Friedel Reiner H W
Title: The energization of relativistic electrons in the outer Van Allen radiation belt
Abstract: The origin and dynamics of the Van Allen radiation belts is one of the longest-standing questions of the space age, and one that is increasingly important for space applications as satellite systems become more sophisticated, smaller and more susceptible to radiation effects. The precise mechanism by which the Earth's magnetosphere is able to accelerate electrons from thermal to ultrarelativistic energies (Edouble greater than0.5 MeV) has been particularly difficult to definitively resolve. The traditional explanation is that large-scale, fluctuating electric and magnetic fields energize particles through radial diffusion1. More recent theories2, 3 and observations4, 5 have suggested that gyro-resonant wave–particle interactions may be comparable to or more important than radial diffusio. . .
Date: 09/2007 Publisher: Nature Physics Pages: 614 - 617 DOI: 10.1038/nphys655 Available at: http://www.nature.com/nphys/journal/v3/n9/full/nphys655.html
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Authors: O’Brien T P, Lorentzen K. R., Mann I. R., Meredith N. P., Blake J. B., et al.
Title: Energization of relativistic electrons in the presence of ULF power and MeV microbursts: Evidence for dual ULF and VLF acceleration
Abstract: We examine signatures of two types of waves that may be involved in the acceleration of energetic electrons in Earth's outer radiation belts. We have compiled a database of ULF wave power from SAMNET and IMAGE ground magnetometer stations for 1987–2001. Long-duration, comprehensive, in situ VLF/ELF chorus wave observations are not available, so we infer chorus wave activity from low-altitude SAMPEX observations of MeV electron microbursts for 1996–2001 since microbursts are thought to be caused by interactions between chorus and trapped electrons. We compare the ULF and microburst observations to in situ trapped electrons observed by high-altitude satellites from 1989–2001. We find that electron acceleration at low L shells is closely associated with both ULF activity and MeV microbu. . .
Date: 08/2003 Publisher: Journal of Geophysical Research DOI: 10.1029/2002JA009784 Available at: http://onlinelibrary.wiley.com/doi/10.1029/2002JA009784/abstract
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Authors: Reeves Geoffrey D, Friedel Reiner H W, Larsen Brian A., Skoug Ruth M., Funsten Herbert O., et al.
Title: Energy dependent dynamics of keV to MeV electrons in the inner zone, outer zone, and slot regions.
Abstract: We present observations of the radiation belts from the HOPE and MagEIS particle detectors on the Van Allen Probes satellites that illustrate the energy-dependence and L-shell dependence of radiation belt enhancements and decays. We survey events in 2013 and analyze an event on March 1 in more detail. The observations show: (a) At all L-shells, lower-energy electrons are enhanced more often than higher energies; (b) Events that fill the slot region are more common at lower energies; (c) Enhancements of electrons in the inner zone are more common at lower energies; and (d) Even when events do not fully fill the slot region, enhancements at lower-energies tend to extend to lower L-shells than higher energies. During enhancement events the outer zone extends to lower L-shells at lower energie. . .
Date: 12/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021569 Available at: http://doi.wiley.com/10.1002/2015JA021569http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015JA021569
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Authors: Turner D. L., Fennell J. F., Blake J B, Clemmons J. H., Mauk B H, et al.
Title: Energy limits of electron acceleration in the plasma sheet during substorms: A case study with the Magnetospheric Multiscale (MMS) mission
Abstract: We present multipoint observations of earthward moving dipolarization fronts and energetic particle injections from NASA's Magnetospheric Multiscale mission with a focus on electron acceleration. From a case study during a substorm on 02 August 2015, we find that electrons are only accelerated over a finite energy range, from a lower energy threshold at ~7–9 keV up to an upper energy cutoff in the hundreds of keV range. At energies lower than the threshold energy, electron fluxes decrease, potentially due to precipitation by strong parallel electrostatic wavefields or initial sources in the lobes. Electrons at energies higher than the threshold are accelerated cumulatively by a series of impulsive magnetic dipolarization events. This case demonstrates how the upper energy cutoff increa. . .
Date: 08/2016 Publisher: Geophysical Research Letters Pages: 7785 - 7794 DOI: 10.1002/2016GL069691 Available at: http://doi.wiley.com/10.1002/2016GL069691
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Authors: Goldsten J O, Maurer R H, Peplowski P N, Holmes-Siedle A G, Herrmann C C, et al.
Title: The Engineering Radiation Monitor for the Radiation Belt Storm Probes Mission
Abstract: An Engineering Radiation Monitor (ERM) has been developed as a supplementary spacecraft subsystem for NASA’s Radiation Belt Storm Probes (RBSP) mission. The ERM will monitor total dose and deep dielectric charging at each RBSP spacecraft in real time. Configured to take the place of spacecraft balance mass, the ERM contains an array of eight dosimeters and two buried conductive plates. The dosimeters are mounted under covers of varying shielding thickness to obtain a dose-depth curve and characterize the electron and proton contributions to total dose. A 3-min readout cadence coupled with an initial sensitivity of ∼0.01 krad should enable dynamic measurements of dose rate throughout the 9-hr RBSP orbit. The dosimeters are Radiation-sensing Field Effect Transistors (RadFETs) and operate. . .
Date: 11/2013 Publisher: Space Science Reviews DOI: 10.1007/s11214-012-9917-x Available at: http://link.springer.com/article/10.1007%2Fs11214-012-9917-x
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Authors: Li Haimeng, Yuan Zhigang, Yu Xiongdong, Huang Shiyong, Wang Dedong, et al.
Title: The enhancement of cosmic radio noise absorption due to hiss-driven energetic electron precipitation during substorms
Abstract: The Van-Allen probes, low-altitude NOAA satellite, MetOp satellite and riometer are used to analyze variations of precipitating energetic electron fluxes and cosmic radio noise absorption (CNA) driven by plasmaspheric hiss with respect to geomagnetic activities. The hiss-driven energetic electron precipitations (at L~4.7-5.3, MLT~8-9) are observed during geomagnetic quiet condition and substorms, respectively. We find that the CNA detected by riometers increased very little in the hiss-driven event during quiet condition on September 06, 2012. The hiss-driven enhancement of riometer was still little during the first substorm on September 30, 2012. However, the absorption detected by the riometer largely increased while the energies of the injected electrons became higher during the second . . .
Date: 06/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021113 Available at: http://doi.wiley.com/10.1002/2015JA021113
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Authors: Goldstein J, De Pascuale S., and Kurth W S
Title: Epoch‐Based Model for Stormtime Plasmapause Location
Abstract: The output of a plasmapause test particle (PTP) code is used to formulate a new epoch‐based plasmapause model. The PTP simulation is run for an ensemble of 60 storms spanning 3 September 2012 to 28 September 2017 and having peak Dst of −60 nT or less, yielding over 7 million model plasmapause locations. Events are automatically identified and epoch times calculated relative to the respective storm peaks. Epoch analysis of the simulated plasmapause is demonstrated to be an effective method to reveal the dynamical phases of plume formation and evolution. The plasmapause radius is found to be strongly correlated with positive solar wind electric field. The epoch‐binned PTP data are used to create the first analytical model of the plasmapause that explicitly includes plumes. We obtain th. . .
Date: 05/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025996 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025996
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Authors: Min Kyungguk, Boardsen Scott A., Denton Richard E, and Liu Kaijun
Title: Equatorial Evolution of the Fast Magnetosonic Mode in the Source Region: Observation-Simulation Comparison of the Preferential Propagation Direction
Abstract: Recent analysis of an event observed by the Van Allen Probes in the source region outside the plasmapause has shown that fast magnetosonic waves (also referred to as equatorial noise) propagate preferentially in the azimuthal direction, implying that wave amplification should occur during azimuthal propagation. To demonstrate this, we carry out 2‐D particle‐in‐cell simulations of the fast magnetosonic mode at the dipole magnetic equator with the simulation box size, the magnetic field inhomogeneity, and the plasma parameters chosen from the same event recently analyzed. The self‐consistently evolving electric and magnetic field fluctuations are characterized by spectral peaks at harmonics of the local proton cyclotron frequency. The azimuthal component of the electric field fluctua. . .
Date: 11/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026037 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026037
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Authors: Němec F., Santolik O, Hrbáčková Z., Pickett J. S., and Cornilleau-Wehrlin N.
Title: Equatorial noise emissions with quasiperiodic modulation of wave intensity
Abstract: Equatorial noise (EN) emissions are electromagnetic wave events at frequencies between the proton cyclotron frequency and the lower hybrid frequency observed in the equatorial region of the inner magnetosphere. They propagate nearly perpendicular to the ambient magnetic field, and they exhibit a harmonic line structure characteristic of the proton cyclotron frequency in the source region. However, they were generally believed to be continuous in time. We investigate more than 2000 EN events observed by the Spatio-Temporal Analysis of Field Fluctuations and Wide-Band Data Plasma Wave investigation instruments on board the Cluster spacecraft, and we show that this is not always the case. A clear quasiperiodic (QP) time modulation of the wave intensity is present in more than 5% of events. We. . .
Date: 04/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020816 Available at: http://doi.wiley.com/10.1002/2014JA020816
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Authors: ěmec F., ík O., Boardsen S. A., Hospodarsky G B, and Kurth W S
Title: Equatorial noise with quasiperiodic modulation: Multipoint observations by the Van Allen Probes spacecraft
Abstract: Electromagnetic wave measurements performed by the two Van Allen Probes spacecraft are used to analyze equatorial noise emissions with a quasiperiodic modulation of the wave intensity. These waves are confined to the vicinity of the geomagnetic equator, and they occur primarily on the dayside. In situ plasma number density measurements are used to evaluate density variations related to the wave occurrence. It is shown that the events are sometimes effectively confined to low density regions, being observed at successive satellite passes over a time duration as long as one hour. The events typically occur outside the plasmasphere, and they are often cease to exist just at the plasmapause. The analysis of the spatial separations of the spacecraft at the times when the events were observed si. . .
Date: 05/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025482 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025482
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Authors: Lyons Lawrence R, and Thorne Richard Mansergh
Title: Equilibrium Structure of Radiation Belt Electrons
Abstract: The detailed quiet time structure of energetic electrons in the earth's radiation belts is explained on the basis of a balance between pitch angle scattering loss and inward radial diffusion from an average outer zone source. Losses are attributed to a combination of classical Coulomb scattering at low L and whistler mode turbulent pitch angle diffusion throughout the outer plasmasphere. Radial diffusion is driven by substorm associated fluctuations of the magnetospheric convection electric field.
Date: 05/1973 Publisher: Journal of Geophysical Research Pages: 2142 - 2149 DOI: 10.1029/JA078i013p02142 Available at: http://onlinelibrary.wiley.com/doi/10.1029/JA078i013p02142/abstract
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Authors: Ozaki Mitsunori, Yagitani Satoshi, Takahashi Ken, Imachi Tomohiko, Koji Hiroki, et al.
Title: Equivalent Circuit Model for the Electric Field Sensitivity of a Magnetic Search Coil of Space Plasma
Abstract: Magnetic search coils (MSCs) are sensitive to both magnetic and electric fields, but detecting electric fields is unnecessary for magnetic observations of plasma waves. However, it is important to evaluate both sensitivities for different geometries and electrostatic shields to avoid electric field pickup. An equivalent circuit model for the electric field sensitivity of an MSC in a collisionless isotropic cold plasma is developed here using electrical coupling through a sheath capacitance. That sensitivity is defined by a relationship between the MSC impedance and the sheath capacitance. To confirm the validity of the circuit model, the sensitivity to an electric field is measured by imposing an external electric field using charged parallel metallic plates in laboratory experiments. The . . .
Date: 10/2014 Publisher: IEEE Sensors Journal Pages: 1 - 1 DOI: 10.1109/JSEN.2014.2365495 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6937067
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Authors: Sarris T. E.
Title: Estimates of the power per mode number of broadband ULF waves at geosynchronous orbit
Abstract: In studies of radial diffusion processes in the magnetosphere it is well known that ultralow frequency (ULF) waves of frequency mωd can resonantly interact with particles of drift frequency ωd, where m is the waves' azimuthal mode number. Due to difficulties in estimating m, an oversimplifying assumption is often made in simulations, namely that all ULF wave power is located at a single mode number. In this paper a technique is presented for extracting information on the distribution of ULF power in a range of azimuthal mode numbers. As a first step, the cross power and phase differences between time series from azimuthally aligned magnetometers are calculated. Subsequently, through integrating the ULF power at particular ranges of phase differences that correspond to particular mode num. . .
Date: 07/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 5539 - 5550 DOI: 10.1002/2013JA019238 Available at: http://doi.wiley.com/10.1002/2013JA019238
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Authors: Bin Kang Suk-, Min Kyoung-Wook, Fok Mei-Ching, Hwang Junga, and Choi Cheong-Rim
Title: Estimation of pitch angle diffusion rates and precipitation time scales of electrons due to EMIC waves in a realistic field model
Abstract: Electromagnetic ion cyclotron (EMIC) waves are closely related to precipitating loss of relativistic electrons in the radiation belts, and thereby, a model of the radiation belts requires inclusion of the pitch angle diffusion caused by EMIC waves. We estimated the pitch angle diffusion rates and the corresponding precipitation time scales caused by H and He band EMIC waves using the Tsyganenko 04 (T04) magnetic field model at their probable regions in terms of geomagnetic conditions. The results correspond to enhanced pitch angle diffusion rates and reduced precipitation time scales compared to those based on the dipole model, up to several orders of magnitude for storm times. While both the plasma density and the magnetic field strength varied in these calculations, the reduction of the . . .
Date: 10/2015 Publisher: Journal of Geophysical Research: Space Physics Pages: 8529 - 8546 DOI: 10.1002/2014JA020644 Available at: http://doi.wiley.com/10.1002/2014JA020644http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2014JA020644
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Authors: Juhász Lilla, Omura Yoshiharu, Lichtenberger János, and Friedel Reinhard H.
Title: Evaluation of Plasma Properties From Chorus Waves Observed at the Generation Region
Abstract: In this study we present an inversion method which provides thermal plasma population parameters from characteristics of chorus emissions only. Our ultimate goal is to apply this method to ground‐based data in order to derive the lower‐energy boundary condition for many radiation belt models. The first step is to test the chorus inversion method on in situ data of the Van Allen Probes in the generation region. The density and thermal velocity of energetic electrons (few kiloelectron volts to 100 keV) are derived from frequency sweep rate and starting frequencies of chorus emissions through analysis of wave data from the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes. The nonlinear wave growth theory of Omura and Nunn (2011, https://doi. . .
Date: 05/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026337 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026337
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Authors: Albert J M
Title: Evaluation of quasi-linear diffusion coefficients for EMIC waves in a multispecies plasma
Abstract: Quasi-linear velocity-space diffusion coefficients due to L-mode electromagnetic ion cyclotron (EMIC) waves are considered in a multispecies plasma. It is shown, with slight approximations to exact cold plasma theory, that within EMIC pass bands the index of refraction is a monotonically increasing function of frequency. Analytical criteria are then derived which identify ranges of latitude, wavenormal angle, and resonance number consistent with resonance in a prescribed wave population. This leads to computational techniques which allow very efficient calculation of the diffusion coefficients, along the lines previously developed for whistler and ion cyclotron waves in an electron-proton plasma. The techniques are applied to radiation belt electrons at L = 4, for EMIC waves in the hydroge. . .
Date: 06/2003 Publisher: Journal of Geophysical Research DOI: 10.1029/2002JA009792 Available at: http://onlinelibrary.wiley.com/doi/10.1029/2002JA009792/abstract
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Authors: Albert J M
Title: Evaluation of quasi-linear diffusion coefficients for whistler mode waves in a plasma with arbitrary density ratio
Abstract: Techniques are presented for efficiently evaluating quasi-linear diffusion coefficients for whistler mode waves propagating according to the full cold plasma index of refraction. In particular, the density ratio ωpe/Ωe can be small, which favors energy diffusion. This generalizes an approach, previously used for high-density hiss and electromagnetic ion cyclotron waves, of identifying (and omitting) ranges of wavenormal angle θ that are incompatible with cyclotron resonant frequencies ω occurring between sharp cutoffs of the modeled wave frequency spectrum. This requires a detailed analysis of the maximum and minimum values of the refractive index as a function of ω and θ, as has previously been performed in the high-density approximation. Sample calculations show the effect of low-d. . .
Date: 03/2005 Publisher: Journal of Geophysical Research DOI: 10.1029/2004JA010844 Available at: http://onlinelibrary.wiley.com/doi/10.1029/2004JA010844/abstract
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Authors: Zhu Hui, Shprits Yuri Y, Chen Lunjin, Liu Xu, and Kellerman Adam C.
Title: An event on simultaneous amplification of exohiss and chorus waves associated with electron density enhancements
Abstract: Whistler mode exohiss are the structureless hiss waves observed outside the plasmapause with featured equatorward Poynting flux. An event of the amplification of exohiss as well as chorus waves was recorded by Van Allen Probes during the recovery phase of a weak geomagnetic storm. Amplitudes of both types of the waves showed a significant increase at the regions of electron density enhancements. It is found that the electrons resonant with exohiss and chorus showed moderate pitch‐angle anisotropies. The ratio of the number of electrons resonating with exohiss to total electron number presented in‐phase correlation with density variations, which suggests that exohiss can be amplified due to electron density enhancement in terms of cyclotron instability. The calculation of linear growth . . .
Date: 10/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2017JA025023 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017JA025023
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Authors: Tu Weichao, Cunningham G. S., Chen Y., Morley S. K., Reeves G D, et al.
Title: Event-specific chorus wave and electron seed population models in DREAM3D using the Van Allen Probes
Abstract: The DREAM3D diffusion model is applied to Van Allen Probes observations of the fast dropout and strong enhancement of MeV electrons during the October 2012 “double-dip” storm. We show that in order to explain the very different behavior in the two “dips,” diffusion in all three dimensions (energy, pitch angle, and L*) coupled with data-driven, event-specific inputs, and boundary conditions is required. Specifically, we find that outward radial diffusion to the solar wind-driven magnetopause, an event-specific chorus wave model, and a dynamic lower-energy seed population are critical for modeling the dynamics. In contrast, models that include only a subset of processes, use statistical wave amplitudes, or rely on inward radial diffusion of a seed population, perform poorly. The resu. . .
Date: 03/2014 Publisher: Geophysical Research Letters Pages: 1359 - 1366 DOI: 10.1002/2013GL058819 Available at: http://doi.wiley.com/10.1002/2013GL058819
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Authors: Meredith Nigel P, Cain Michelle, Horne Richard B., Thorne Richard M., Summers D., et al.
Title: Evidence for chorus-driven electron acceleration to relativistic energies from a survey of geomagnetically disturbed periods
Abstract: We perform a survey of the plasma wave and particle data from the CRRES satellite during 26 geomagnetically disturbed periods to investigate the viability of a local stochastic electron acceleration mechanism to relativistic energies driven by Doppler-shifted cyclotron resonant interactions with whistler mode chorus. Relativistic electron flux enhancements associated with moderate or strong storms may be seen over the whole outer zone (3 < L < 7), typically peaking in the range 4 < L < 5, whereas those associated with weak storms and intervals of prolonged substorm activity lacking a magnetic storm signature (PSALMSS) are typically observed further out in the regions 4 < L < 7 and 4.5 < L < 7, respectively. The most significant relativistic electron flux enhancements are seen outside of th. . .
Date: 06/2003 Publisher: Journal of Geophysical Research DOI: 10.1029/2002JA009764 Available at: http://onlinelibrary.wiley.com/doi/10.1029/2002JA009764/abstract
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Authors: Dai Lei, Wygant John R., Cattell Cynthia A., Thaller Scott, Kersten Kris, et al.
Title: Evidence for injection of relativistic electrons into the Earth's outer radiation belt via intense substorm electric fields
Abstract: Observation and model results accumulated in the last decade indicate that substorms can promptly inject relativistic ‘killer’ electrons (≥MeV) in addition to 10–100 keV subrelativistic populations. Using measurements from Cluster, Polar, LANL, and GOES satellites near the midnight sector, we show in two events that intense electric fields, as large as 20 mV/m, associated with substorm dipolarization are associated with injections of relativistic electrons into the outer radiation belt. Enhancements of hundreds of keV electrons at dipolarization in the magnetotail can account for the injected MeV electrons through earthward transport. These observations provide evidence that substorm electric fields inject relativistic electrons by transporting magnetotail electrons into the outer . . .
Date: 02/2014 Publisher: Geophysical Research Letters Pages: 1133 - 1141 DOI: 10.1002/2014GL059228 Available at: http://doi.wiley.com/10.1002/2014GL059228
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Authors: Shumko Mykhaylo, Turner Drew L, O'Brien T P, Claudepierre Seth G., Sample John, et al.
Title: Evidence of Microbursts Observed Near the Equatorial Plane in the Outer Van Allen Radiation Belt
Abstract: We present the first evidence of electron microbursts observed near the equatorial plane in Earth's outer radiation belt. We observed the microbursts on March 31st, 2017 with the Magnetic Electron Ion Spectrometer and RBSP Ion Composition Experiment on the Van Allen Probes. Microburst electrons with kinetic energies of 29‐92 keV were scattered over a substantial range of pitch angles, and over time intervals of 150‐500 ms. Furthermore, the microbursts arrived without dispersion in energy, indicating that they were recently scattered near the spacecraft. We have applied the relativistic theory of wave‐particle resonant diffusion to the calculated phase space density, revealing that the observed transport of microburst electrons is not consistent with the hypothesized quasi‐linear ap. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078451 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078451
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Authors: Li W, Mourenas D., Artemyev A., Agapitov O., Bortnik J, et al.
Title: Evidence of stronger pitch angle scattering loss caused by oblique whistler-mode waves as compared with quasi-parallel waves
Abstract: Wave normal distributions of lower-band whistler-mode waves observed outside the plasmapause exhibit two peaks; one near the parallel direction and the other at very oblique angles. We analyze a number of conjunction events between the Van Allen Probes near the equatorial plane and POES satellites at conjugate low altitudes, where lower-band whistler-mode wave amplitudes were inferred from the two-directional POES electron measurements over 30–100 keV, assuming that these waves were quasi-parallel. For conjunction events, the wave amplitudes inferred from the POES electron measurements were found to be overestimated as compared with the Van Allen Probes measurements primarily for oblique waves and quasi-parallel waves with small wave amplitudes (< ~20 pT) measured at low latitudes. This . . .
Date: 08/2014 Publisher: Geophysical Research Letters Pages: n/a - n/a DOI: 10.1002/2014GL061260 Available at: http://doi.wiley.com/10.1002/2014GL061260
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Authors: Thorne R M, Li W, Ni B, Ma Q, Bortnik J, et al.
Title: Evolution and slow decay of an unusual narrow ring of relativistic electrons near L ~ 3.2 following the September 2012 magnetic storm
Abstract: A quantitative analysis is performed on the decay of an unusual ring of relativistic electrons between 3 and 3.5 RE, which was observed by the Relativistic Electron Proton Telescope instrument on the Van Allen probes. The ring formed on 3 September 2012 during the main phase of a magnetic storm due to the partial depletion of the outer radiation belt for L > 3.5, and this remnant belt of relativistic electrons persisted at energies above 2 MeV, exhibiting only slow decay, until it was finally destroyed during another magnetic storm on 1 October. This long-term stability of the relativistic electron ring was associated with the rapid outward migration and maintenance of the plasmapause to distances greater than L = 4. The remnant ring was thus immune from the dynamic process, whic. . .
Date: 06/2013 Publisher: Geophysical Research Letters DOI: 10.1002/grl.50627 Available at: http://onlinelibrary.wiley.com/doi/10.1002/grl.50627/full
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Authors: Bingley L., Angelopoulos V, Sibeck D., Zhang X., and Halford A.
Title: The Evolution of a Pitch‐Angle “Bite‐Out” Scattering Signature Caused by EMIC Wave Activity: A Case Study
Abstract: Electromagnetic ion cyclotron (EMIC) waves are understood to be one of the dominant drivers of relativistic electron loss from Earth's radiation belts. Theory predicts that the associated gyroresonant wave‐particle interaction results in a distinct energy‐dependent “bite‐out” signature in the normalized flux distribution of electrons as they are scattered into the loss cone. We identify such signatures along with the responsible EMIC waves captured in situ by the Van Allen Probes on 15–16 February 2017. Using the cold plasma approximation, we predict the pitch‐angle cutoffs for the scattering signature for the captured EMIC wave and find it in good agreement with the observed electron bite‐out scattering signature. Employing the close conjunction between the Van Allen Probe. . .
Date: 06/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026292 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026292
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Authors: Zhou Qinghua, Xiao Fuliang, Yang Chang, Liu Si, He Yihua, et al.
Title: Evolution of chorus emissions into plasmaspheric hiss observed by Van Allen Probes
Abstract: The two classes of whistler mode waves (chorus and hiss) play different roles in the dynamics of radiation belt energetic electrons. Chorus can efficiently accelerate energetic electrons, and hiss is responsible for the loss of energetic electrons. Previous studies have proposed that chorus is the source of plasmaspheric hiss, but this still requires an observational confirmation because the previously observed chorus and hiss emissions were not in the same frequency range in the same time. Here we report simultaneous observations form Van Allen Probes that chorus and hiss emissions occurred in the same range ∼300–1500 Hz with the peak wave power density about 10−5 nT2/Hz during a weak storm on 3 July 2014. Chorus emissions propagate in a broad region outside the plasmapause. Meanwhi. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: 4518 - 4529 DOI: 10.1002/2016JA022366 Available at: http://doi.wiley.com/10.1002/2016JA022366
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Authors: Vainchtein D., Zhang X.-J., Artemyev A. V., Mourenas D., Angelopoulos V, et al.
Title: Evolution of electron distribution driven by nonlinear resonances with intense field-aligned chorus waves
Abstract: Resonant electron interaction with whistler‐mode chorus waves is recognized as one of the main drivers of radiation belt dynamics. For moderate wave intensity, this interaction is well described by quasi‐linear theory. However, recent statistics of parallel propagating chorus waves have demonstrated that 5 − 20% of the observed waves are sufficiently intense to interact nonlinearly with electrons. Such interactions include phase trapping and phase bunching (nonlinear scattering) effects not described by quasi‐linear diffusion. For sufficiently long (large) wave‐packets, these nonlinear effects can result in very rapid electron acceleration and scattering. In this paper we introduce a method to include trapping and nonlinear scattering into the kinetic equation describing the . . .
Date: 09/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025654 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025654
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Authors: Ganguli G., Crabtree C., Mithaiwala M., Rudakov L., and Scales W.
Title: Evolution of lower hybrid turbulence in the ionosphere
Abstract: Three-dimensional evolution of the lower hybrid turbulence driven by a spatially localized ion ring beam perpendicular to the ambient magnetic field in space plasmas is analyzed. It is shown that the quasi-linear saturation model breaks down when the nonlinear rate of scattering by thermal electron is larger than linear damping rates, which can occur even for low wave amplitudes. The evolution is found to be essentially a three-dimensional phenomenon, which cannot be accurately explained by two-dimensional simulations. An important feature missed in previous studies of this phenom- enon is the nonlinear conversion of electrostatic lower hybrid waves into electromagnetic whistler and magnetosonic waves and the consequent energy loss due to radiation from the source region. This can result i. . .
Date: 11/2015 Publisher: Physics of Plasmas Pages: 112904 DOI: 10.1063/1.4936281 Available at: http://scitation.aip.org/content/aip/journal/pop/22/11/10.1063/1.4936281
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Authors: Nishimura Y., Bortnik J, Li W, Lyons L R, Donovan E. F., et al.
Title: Evolution of nightside subauroral proton aurora caused by transient plasma sheet flows
Abstract: While nightside subauroral proton aurora shows rapid temporal variations, the cause of this variability has rarely been investigated. Using well-coordinated observations by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imagers, THEMIS satellites in the equatorial magnetosphere, and the low-altitude NOAA 17 satellite, we examined the rapid temporal evolution of subauroral proton aurora in the premidnight sector. An isolated proton aurora occurred soon after an auroral poleward boundary intensification that was followed by an auroral streamer reaching the equatorward boundary of the auroral oval. Three THEMIS satellites in the magnetotail detected flow bursts and one of the THEMIS satellites in the outer plasmasphere observed a ring current injectio. . .
Date: 07/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 5295 - 5304 DOI: 10.1002/2014JA020029 Available at: http://doi.wiley.com/10.1002/2014JA020029
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Authors: Jaynes A. N., Li X, Schiller Q. G., Blum L. W., Tu W., et al.
Title: Evolution of relativistic outer belt electrons during an extended quiescent period
Abstract: To effectively study steady loss due to hiss-driven precipitation of relativistic electrons in the outer radiation belt, it is useful to isolate this loss by studying a time of relatively quiet geomagnetic activity. We present a case of initial enhancement and slow, steady decay of 700 keV - 2 MeV electron populations in the outer radiation belt during an extended quiescent period from ~15 December 2012 - 13 January 2013. We incorporate particle measurements from a constellation of satellites, including the Colorado Student Space Weather Experiment (CSSWE) CubeSat, the Van Allen Probes twin spacecraft, and THEMIS, to understand the evolution of the electron populations across pitch angle and energy. Additional data from calculated phase space density (PSD), as well as hiss and chorus w. . .
Date: 12/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020125 Available at: http://doi.wiley.com/10.1002/2014JA020125
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Authors: Zhao H., Li X, Baker D N, Fennell J. F., Blake J B, et al.
Title: The evolution of ring current ion energy density and energy content during geomagnetic storms based on Van Allen Probes measurements
Abstract: Enabled by the comprehensive measurements from the MagEIS, HOPE, and RBSPICE instruments onboard Van Allen Probes in the heart of the radiation belt, the relative contributions of ions with different energies and species to the ring current energy density and their dependence on the phases of geomagnetic storms are quantified. The results show that lower energy (<50 keV) protons enhance much more often and also decay much faster than higher energy protons. During the storm main phase, ions with energies < 50 keV contribute more significantly to the ring current than those with higher energies; while the higher energy protons dominate during the recovery phase and quiet times. The enhancements of higher energy proton fluxes as well as energy content generally occur later than those of lower. . .
Date: 08/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021533 Available at: http://doi.wiley.com/10.1002/2015JA021533
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Authors: Denton M. H., Thomsen M F, Reeves G D, Larsen B A, Henderson M G, et al.
Title: The Evolution of the Plasma Sheet Ion Composition: Storms and Recoveries
Abstract: The ion plasma sheet (~few hundred eV to ~few 10s keV) is usually dominated by H+ ions. Here, changes in ion composition within the plasma sheet are explored both during individual events, and statistically during 54 calm-to-storm events and during 21 active-to-calm events. Ion composition data from the HOPE (Helium, Oxygen, Proton, Electron) instruments onboard Van Allen Probes satellites provide exceptional spatial and temporal resolution of the H+, O+, and He+ ion fluxes in the plasma sheet. H+ shown to be the dominant ion in the plasma sheet in the calm-to-storm transition. However, the energy-flux of each ion changes in a quasi-linear manner during extended calm intervals. Heavy ions (O+ and He+) become increasingly important during such periods as charge-exchange reactions result in . . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024475 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024475/full
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Authors: Zanetti L. J., Mauk B H, Fox N.J., Barnes R.J., Weiss M, et al.
Title: The Evolving Space Weather System - Van Allen Probes Contribution
Abstract: The overarching goal and purpose of the study of space weather is clear - to understand and address the issues caused by solar disturbances on humans and technological systems. Space weather has evolved in the past few decades from a collection of concerned agencies and researchers to a critical function of the National Weather Service of NOAA. The general effects have also evolved from the well-known telegraph disruptions of the mid-1800’s to modern day disturbances of the electric power grid, communications and navigation, human spaceflight and spacecraft systems. The last two items in this list, and specifically the effects of penetrating radiation, were the impetus for the space weather broadcast implemented on NASA’s Van Allen Probes’ twin pair of satellites, launched in August . . .
Date: 10/2014 Publisher: Space Weather DOI: 10.1002/2014SW001108 Available at: http://doi.wiley.com/10.1002/2014SW001108
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Authors: Thomas Evan G., Yan Jingye, Zhang Jiaojiao, Baker Joseph B. H., Ruohoniemi Michael, et al.
Title: An examination of the source of decameter-scale irregularities in the geomagnetically disturbed mid-latitude ionosphere
Abstract: We present first results from a study of the plasma instability mechanism responsible for the small-scale (∼10 m) ionospheric density irregularities commonly observed by the Super Dual Auroral Radar Network (SuperDARN) HF radars in the vicinity of Sub Auroral Polarization Streams (SAPS) during periods of geomagnetic disturbance. A focus is placed on the mid-latitude region of the ionosphere over North America where recent expansion of the SuperDARN network allows for extensive direct comparisons with total electron content (TEC) measurements from a dense network of ground-based GPS receivers. The TEC observations indicate that high-speed SAPS channels and the associated small-scale irregularities are typically located within the mid-latitude ionospheric trough. The Millstone Hill Incoher. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929853 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929853
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Authors: Turner D. L., Lee J. H., Claudepierre S G, Fennell J. F., Blake J B, et al.
Title: Examining coherency scales, substructure, and propagation of whistler-mode chorus elements with Magnetospheric Multiscale (MMS)
Abstract: Whistler-mode chorus waves are a naturally occurring electromagnetic emission observed in Earth's magnetosphere. Here, for the first time, data from NASA's Magnetospheric Multiscale (MMS) mission were used to analyze chorus waves in detail, including the calculation of chorus wave normal vectors, k. A case study was examined from a period of substorm activity around the time of a conjunction between the MMS constellation and NASA's Van Allen Probes mission on 07 April 2016. Chorus wave activity was simultaneously observed by all six spacecraft over a broad range of L-shells (5.5 < L < 8.5), magnetic local time (06:00 < MLT < 09:00), and magnetic latitude (-32° < MLat < -15°), implying a large chorus active region. Eight chorus elements and their substructure were analyzed in detail with . . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024474 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024474/full
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Authors: Zhang J.-C., Saikin A. A., Kistler L. M., Smith C W, Spence H E, et al.
Title: Excitation of EMIC waves detected by the Van Allen Probes on 28 April 2013
Abstract: We report the wave observations, associated plasma measurements, and linear theory testing of electromagnetic ion cyclotron (EMIC) wave events observed by the Van Allen Probes on 28 April 2013. The wave events are detected in their generation regions as three individual events in two consecutive orbits of Van Allen Probe-A, while the other spacecraft, B, does not detect any significant EMIC wave activity during this period. Three overlapping H+ populations are observed around the plasmapause when the waves are excited. The difference between the observational EMIC wave growth parameter (Σh) and the theoretical EMIC instability parameter (Sh) is significantly raised, on average, to 0.10 ± 0.01, 0.15 ± 0.02, and 0.07 ± 0.02 during the three wave events, respectively. On Van A. . .
Date: 06/2014 Publisher: Geophysical Research Letters Pages: 4101–4108 DOI: 10.1002/2014GL060621 Available at: http://doi.wiley.com/10.1002/2014GL060621
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Authors: Yu Xiongdong, Yuan Zhigang, Huang Shiyong, Yao Fei, Qiao Zheng, et al.
Title: Excitation of extremely low-frequency chorus emissions: The role of background plasma density
Abstract: Low‐frequency chorus emissions have recently attracted much attention due to the suggestion that they may play important roles in the dynamics of the Van Allen Belts. However, the mechanism (s) generating these low‐frequency chorus emissions have not been well understood. . In this letter, we report an interesting case in which background plasma density lowered the lower cutoff frequency of chorus emissions from above 0.1 f ce (typical ordinary chorus) to 0.02 f ce (extremely low‐frequency chorus). Those extremely low‐frequency chorus waves were observed in a rather dense plasma, where the number density N e was found to be several times larger than has been associated with observations of ordinary chorus waves. For suprathermal electrons whose free energy is supplied by anisotropi. . .
Date: 02/2019 Publisher: Earth and Planetary Physics Pages: 1 - 7 DOI: 10.26464/epp2019001 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.26464/epp2019001
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Authors: Zhou Qinghua, Xiao Fuliang, Yang Chang, Liu Si, Kletzing C A, et al.
Title: Excitation of nightside magnetosonic waves observed by Van Allen Probes
Abstract: During the recovery phase of the geomagnetic storm on 30-31 March 2013, Van Allen Probe A detected enhanced magnetosonic (MS) waves in a broad range of L =1.8-4.7 and MLT =17-22 h, with a frequency range ~10-100 Hz. In the meanwhile, distinct proton ring distributions with peaks at energies of ~10 keV, were also observed in L =3.2-4.6 and L =5.0-5.6. Using a subtracted bi-Maxwellian distribution to model the observed proton ring distribution, we perform three dimensional ray tracing to investigate the instability, propagation and spatial distribution of MS waves. Numerical results show that nightside MS waves are produced by proton ring distribution and grow rapidly from the source location L =5.6 to the location L =5.0, but remain nearly stable at locations L <5.0 Moreover, waves launched. . .
Date: 11/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2014JA020481 Available at: http://doi.wiley.com/10.1002/2014JA020481
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