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Authors: Crabtree C., Rudakov L., Ganguli G., Mithaiwala M., Galinsky V., et al.
Title: Weak turbulence in the magnetosphere: Formation of whistler wave cavity by nonlinear scattering
Abstract: We consider the weak turbulence of whistler waves in the in low-β inner magnetosphere of the earth. Whistler waves, originating in the ionosphere, propagate radially outward and can trigger nonlinear induced scattering by thermal electrons provided the wave energy density is large enough. Nonlinear scattering can substantially change the direction of the wave vector of whistler waves and hence the direction of energy flux with only a small change in the frequency. A portion of whistler waves return to the ionosphere with a smaller perpendicular wave vector resulting in diminished linear damping and enhanced ability to pitch-angle scatter trapped electrons. In addition, a portion of the scatteredwave packets can be reflected near the ionosphere back into the magnetosphere. Through multiple. . .
Date: 01/2012 Publisher: Physics of Plasmas Pages: 032903 DOI: 10.1063/1.3692092 Available at: http://scitation.aip.org/content/aip/journal/pop/19/3/10.1063/1.3692092
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Authors: Crabtree Chris, Tejero Erik, Ganguli Gurudas, Hospodarsky George B., and Kletzing Craig A.
Title: Bayesian Spectral Analysis of Chorus Sub-Elements from the Van Allen Probes
Abstract: We develop a Bayesian spectral analysis technique that calculates the probability distribution functions of a superposition of wave-modes each described by a linear growth rate, a frequency and a chirp rate. The Bayesian framework has a number of advantages, including 1) reducing the parameter space by integrating over the amplitude and phase of the wave, 2) incorporating the data from each channel to determine the model parameters such as frequency which leads to high resolution results in frequency and time, 3) the ability to consider the superposition of waves where the wave-parameters are closely spaced, 4) the ability to directly calculate the expectation value of wave parameters without resorting to ensemble averages, 5) the ability to calculate error bars on model parameters. We exa. . .
Date: 04/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023547 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023547/full
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Authors: Crabtree Chris, Ganguli Gurudas, and Tejero Erik
Title: Analysis of self-consistent nonlinear wave-particle interactions of whistler waves in laboratory and space plasmas
Abstract: Whistler mode chorus is one of the most important emissions affecting the energization of the radiation belts. Recent laboratory experiments that inject energetic electron beams into a cold plasma have revealed several spectral features in the nonlinear evolution of these instabilities that have also been observed in high-time resolution in situ wave-form data. These features include (1) a sub-element structure which consists of an amplitude modulation on time-scales slower than the bounce time, (2) closely spaced discrete frequency hopping that results in a faster apparent frequency chirp rate, (3) fast frequency changes near the sub-element boundaries, and (4) harmonic generation. In this paper, we develop a finite dimensional self-consistent Hamiltonian model for the evolution of the re. . .
Date: 03/2017 Publisher: Physics of Plasmas Pages: 056501 DOI: 10.1063/1.4977539 Available at: http://aip.scitation.org/doi/10.1063/1.4977539
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Authors: Contel O., Nakamura R, Breuillard H., Argall M. R., Graham D. B., et al.
Title: Lower-hybrid drift waves and electromagnetic electron space-phase holes associated with dipolarization fronts and field-aligned currents observed by the Magnetospheric Multiscale mission during a substorm
Abstract: We analyse two ion scale dipolarization fronts associated with field-aligned currents detected by the Magnetospheric Multiscale mission during a large substorm on August 10, 2016. The first event corresponds to a fast dawnward flow with an anti-parallel current and could be generated by the wake of a previous fast earthward flow. It is associated with intense lower-hybrid drift waves detected at the front and propagating dawnward with a perpendicular phase speed close to the electric drift and the ion thermal velocity. The second event corresponds to a flow reversal: from southwward/dawnward to northward/duskward associated with a parallel current consistent with a brief expansion of the plasma sheet before the front crossing, and with a smaller lower-hybrid drift wave activity. Electromag. . .
Date: 10/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024550 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024550/full
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Authors: Colpitts C. A., Cattell C. A., Engebretson M., Broughton M., Tian S., et al.
Title: Van Allen Probes observations of cross-scale coupling between electromagnetic ion cyclotron waves and higher-frequency wave modes
Abstract: We present observations of higher-frequency (~50–2500 Hz, ~0.1–0.7 fce) wave modes modulated at the frequency of colocated lower frequency (0.5–2 Hz, on the order of fci) waves. These observations come from the Van Allen Probes Electric Field and Waves instrument's burst mode data and represent the first observations of coupling between waves in these frequency ranges. The higher-frequency wave modes, typically whistler mode hiss and chorus or magnetosonic waves, last for a few to a few tens of seconds but are in some cases observed repeatedly over several hours. The higher-frequency waves are observed to be unmodulated before and after the presence of the electromagnetic ion cyclotron (EMIC) waves, but when the EMIC waves are present, the amplitude of the higher-frequency waves . . .
Date: 11/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL071566 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071566/full
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Authors: Coleman Tim, McCollough James, Young Shawn, and Rigler E. J.
Title: Operational Nowcasting of Electron Flux Levels in the Outer Zone of Earth's Radiation Belt
Abstract: We describe a lightweight, accurate nowcasting model for electron flux levels measured by the Van Allen probes. Largely motivated by Rigler et al. [2004], we turn to a time‐varying linear filter of previous flux levels and Kp. We train and test this model on data gathered from the 2.10 MeV channel of the Relativistic Electron‐Proton Telescope (REPT) sensor onboard the Van Allen probes. Dynamic linear models are a specific case of state space models, and can be made flexible enough to emulate the nonlinear behavior of particle fluxes within the radiation belts. Real‐time estimation of the parameters of the model is done using a Kalman Filter, where the state of the model is exactly the parameters. Nowcast performance is assessed against several baseline interpolation schemes. Our mode. . .
Date: 04/2018 Publisher: Space Weather DOI: 10.1029/2017SW001788 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017SW001788
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Authors: Cohen Ian J., Mitchell Donald G., Kistler Lynn M., Mauk Barry H., Anderson Brian J., et al.
Title: Dominance of high energy (>150 keV) heavy ion intensities in Earth's middle to outer magnetosphere
Abstract: Previous observations have driven the prevailing assumption in the field that energetic ions measured by an instrument using a bare solid state detector (SSD) are predominantly protons. However, new near-equatorial energetic particle observations obtained between 7 and 12 RE during Phase 1 of the Magnetospheric Multiscale (MMS) mission challenge the validity of this assumption. In particular, measurements by the Energetic Ion Spectrometer (EIS) instruments have revealed that the intensities of heavy ion species (specifically oxygen and helium) dominate those of protons at energies math formula150-220 keV in the middle to outer (>7 RE) magnetosphere. Given that relative composition measurements can drift as sensors degrade in gain, quality cross-calibration agreement between EIS observation. . .
Date: 08/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024351 Available at: onlinelibrary.wiley.com/doi/10.1002/2017JA024351/full
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Authors: Cohen Ross, Gerrard Andrew J., Lanzerotti Louis J., Soto-Chavez A. R., Kim Hyomin, et al.
Title: Climatology of high-β plasma measurements in Earth's inner magnetosphere
Abstract: Since their launch in August 2012, the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instruments on the NASA Van Allen Probes spacecraft have been making continuous high-resolution measurements of Earth's ring current plasma environment. After a full traversal through all magnetic local times, a climatology (i.e., a survey of observations) of high-beta (β) plasma events (defined here as β > 1) as measured by the RBSPICE instrument in the ∼45 keV to ∼600 keV proton energy range in the inner magnetosphere (L < 5.8) has been constructed. In this paper we report this climatology of such high-β plasma occurrences, durations, and their general characteristics. Specifically, we show that most high-β events in the RBSPICE energy range are associated with postdusk/premidni. . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022513 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA022513
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Authors: Cohen Ross, Gerrard Andrew, Lanzerotti Louis, Soto-Chavez A. R., Kim Hyomin, et al.
Title: Climatology of high β plasma measurements in Earth's inner magnetosphere
Abstract: Since their launch in August 2012, the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instruments on the NASA Van Allen Probes spacecraft have been making continuous high resolution measurements of Earth's ring current plasma environment. After a full traversal through all magnetic local times, a climatology (i.e., a survey of observations) of high beta (β) plasma events (defined here as β>1) as measured by the RBSPICE instrument in the ∼45-keV to ∼600-keV proton energy range in the inner magnetosphere (L<5.8) has been constructed. In this paper we report this climatology of such high β plasma occurrences, durations, and their general characteristics. Specifically, we show that most high β events in the RBSPICE energy range are associated with post-dusk/pre-midnigh. . .
Date: 12/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022513 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA022513/full
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Authors: Clilverd Mark A., Duthie Roger, Hardman Rachael, Hendry Aaron T., Rodger Craig J., et al.
Title: Electron precipitation from EMIC waves: a case study from 31 May 2013
Abstract: On 31 May 2013 several rising-tone electromagnetic ion-cyclotron (EMIC) waves with intervals of pulsations of diminishing periods (IPDP) were observed in the magnetic local time afternoon and evening sectors during the onset of a moderate/large geomagnetic storm. The waves were sequentially observed in Finland, Antarctica, and western Canada. Co-incident electron precipitation by a network of ground-based Antarctic Arctic Radiation-belt Dynamic Deposition VLF Atmospheric Research Konsortia (AARDDVARK) and riometer instruments, as well as the Polar-orbiting Operational Environmental Satellite (POES) electron telescopes, was also observed. At the same time POES detected 30-80 keV proton precipitation drifting westwards at locations that were consistent with the ground-based observations, i. . .
Date: 04/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021090 Available at: http://doi.wiley.com/10.1002/2015JA021090
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Authors: Claudepierre S G, O'Brien T P, Looper M D, Blake J B, Fennell J. F., et al.
Title: A Revised Look at Relativistic Electrons in the Earth's Inner Radiation Zone and Slot Region
Abstract: We describe a new, more accurate procedure for estimating and removing inner zone background contamination from Van Allen Probes Magnetic Electron Ion Spectrometer (MagEIS) radiation belt measurements. This new procedure is based on the underlying assumption that the primary source of background contamination in the electron measurements at L shells less than three, energetic inner belt protons, is relatively stable. Since a magnetic spectrometer can readily distinguish between foreground electrons and background signals, we are able to exploit the proton stability to construct a model of the background contamination in each MagEIS detector by only considering times when the measurements are known to be background dominated. We demonstrate, for relativistic electron measurements in the inn. . .
Date: 01/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026349 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026349
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Authors: Claudepierre S G, O'Brien T P, Fennell J. F., Blake J B, Clemmons J. H., et al.
Title: The hidden dynamics of relativistic electrons (0.7-1.5 MeV) in the inner zone and slot region
Abstract: We present measurements of relativistic electrons (0.7–1.5 MeV) in the inner zone and slot region obtained by the Magnetic Electron and Ion Spectrometer (MagEIS) instrument on Van Allen Probes. The data presented are corrected for background contamination, which is primarily due to inner-belt protons in these low-L regions. We find that ∼1 MeV electrons were transported into the inner zone following the two largest geomagnetic storms of the Van Allen Probes era to date, the March and June 2015 events. As ∼1 MeV electrons were not observed in Van Allen Probes data in the inner zone prior to these two events, the injections created a new inner belt that persisted for at least 1.5 years. In contrast, we find that electrons injected into the slot region decay on much faster timescales, a. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023719 Available at: http://doi.wiley.com/10.1002/2016JA023719
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Authors: Claudepierre S G, O'Brien T P, Blake J B, Fennell J. F., Roeder J. L., et al.
Title: A background correction algorithm for Van Allen Probes MagEIS electron flux measurements
Abstract: We describe an automated computer algorithm designed to remove background contamination from the Van Allen Probes MagEIS electron flux measurements. We provide a detailed description of the algorithm with illustrative examples from on-orbit data. We find two primary sources of background contamination in the MagEIS electron data: inner zone protons and bremsstrahlung X-rays generated by energetic electrons interacting with the spacecraft material. Bremsstrahlung X-rays primarily produce contamination in the lower energy MagEIS electron channels (~30-500 keV) and in regions of geospace where multi-MeV electrons are present. Inner zone protons produce contamination in all MagEIS energy channels at roughly L < 2.5. The background corrected MagEIS electron data produce a more accurate me. . .
Date: 06/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021171 Available at: http://doi.wiley.com/10.1002/2015JA021171
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Authors: Claudepierre S G, Mann I R, Takahashi K, Fennell J F, Hudson M K, et al.
Title: Van Allen Probes observation of localized drift-resonance between poloidal mode ultra-low frequency waves and 60 keV electrons
Abstract: [1] We present NASA Van Allen Probes observations of wave-particle interactions between magnetospheric ultra-low frequency (ULF) waves and energetic electrons (20–500 keV) on 31 October 2012. The ULF waves are identified as the fundamental poloidal mode oscillation and are excited following an interplanetary shock impact on the magnetosphere. Large amplitude modulations in energetic electron flux are observed at the same period (≈ 3 min) as the ULF waves and are consistent with a drift-resonant interaction. The azimuthal mode number of the interacting wave is estimated from the electron measurements to be ~40, based on an assumed symmetric drift resonance. The drift-resonant interaction is observed to be localized and occur over 5–6 wave cycles, demonstrating peak electron flux modul. . .
Date: 09/2013 Publisher: Geophysical Research Letters Pages: 4491–4497 DOI: 10.1002/grl.50901 Available at: http://onlinelibrary.wiley.com/doi/10.1002/grl.50901/full
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Authors: Claudepierre S G, O'Brien T P, Fennell J. F., Blake J B, Clemmons J. H., et al.
Title: The hidden dynamics of relativistic electrons (0.7-1.5 MeV) in the inner zone and slot region
Abstract: We present measurements of relativistic electrons (0.7–1.5 MeV) in the inner zone and slot region obtained by the Magnetic Electron and Ion Spectrometer (MagEIS) instrument on Van Allen Probes. The data presented are corrected for background contamination, which is primarily due to inner-belt protons in these low-L regions. We find that ∼1 MeV electrons were transported into the inner zone following the two largest geomagnetic storms of the Van Allen Probes era to date, the March and June 2015 events. As ∼1 MeV electrons were not observed in Van Allen Probes data in the inner zone prior to these two events, the injections created a new inner belt that persisted for at least 1.5 years. In contrast, we find that electrons injected into the slot region decay on much faster timescales, a. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023719 Available at: http://doi.wiley.com/10.1002/2016JA023719http://onlinelibrary.wiley.com/wol1/doi/10.1002/2016JA023719
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Authors: Chu X., Bortnik J, Li W, Ma Q, Denton R., et al.
Title: A neural network model of three-dimensional dynamic electron density in the inner magnetosphere
Abstract: A plasma density model of the inner magnetosphere is important for a variety of applications including the study of wave-particle interactions, and wave excitation and propagation. Previous empirical models have been developed under many limiting assumptions and do not resolve short-term variations, which are especially important during storms. We present a three-dimensional dynamic electron density (DEN3D) model developed using a feedforward neural network with electron densities obtained from four satellite missions. The DEN3D model takes spacecraft location and time series of solar and geomagnetic indices (F10.7, SYM-H, and AL) as inputs. It can reproduce the observed density with a correlation coefficient of 0.95 and predict test data set with error less than a factor of 2. Its predict. . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024464 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024464/full
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Authors: Cho Junghee, Lee Dae-Young, Kim Jin-Hee, Shin Dae-Kyu, Kim Kyung-Chan, et al.
Title: New model fit functions of the plasmapause location determined using THEMIS observations during the ascending phase of Solar Cycle 24
Abstract: It is well known that the plasmapause is influenced by the solar wind and magnetospheric conditions. Empirical models of its location have been previously developed such as those by O'Brien and Moldwin (2003) and Larsen et al. (2006). In this study, we identified the locations of the plasmapause using the plasma density data obtained from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. We used the data for the period (2008–2012) corresponding to the ascending phase of Solar Cycle 24. Our database includes data from over a year of unusually weak solar wind conditions, correspondingly covering the plasmapause locations in a wider L range than those in previous studies. It also contains many coronal hole stream intervals during which the plasmasp. . .
Date: 04/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021030 Available at: http://doi.wiley.com/10.1002/2015JA021030
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Authors: Cho J.-H., Lee D.-Y., Noh S.-J., Shin D.-K., Hwang J., et al.
Title: Van Allen Probes Observations of Electromagnetic Ion Cyclotron Waves Triggered by Enhanced Solar Wind Dynamic Pressure
Abstract: Magnetospheric compression due to impact of enhanced solar wind dynamic pressure Pdyn has long been considered as one of the generation mechanisms of electromagnetic ion cyclotron (EMIC) waves. With the Van Allen Probe-A observations, we identify three EMIC wave events that are triggered by Pdyn enhancements under prolonged northward IMF quiet time preconditions. They are in contrast to one another in a few aspects. Event 1 occurs in the middle of continuously increasing Pdyn while Van Allen Probe-A is located outside the plasmapause at post-midnight and near the equator (magnetic latitude (MLAT) ~ -3o). Event 2 occurs by a sharp Pdyn pulse impact while Van Allen Probe-A is located inside the plasmapause in the dawn sector and rather away from the equator (MLAT ~ 12o). Event 3 is c. . .
Date: 09/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022841 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA022841/full
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Authors: Cho J.-H., Lee D.-Y., Noh S.-J., Kim H., Choi C. R., et al.
Title: Spatial dependence of electromagnetic ion cyclotron waves triggered by solar wind dynamic pressure enhancements
Abstract: In this paper, using the multisatellite (the Van Allen Probes and two GOES satellites) observations in the inner magnetosphere, we examine two electromagnetic ion cyclotron (EMIC) wave events that are triggered by Pdyn enhancements under prolonged northward interplanetary magnetic field quiet time preconditions. For both events, the impact of enhanced Pdyn causes EMIC waves at multiple points. However, we find a strong spatial dependence that EMIC waves due to enhanced Pdyn impact can occur at multiple points (likely globally but not necessarily everywhere) but with different wave properties. For Event 1, three satellites situated at a nearly same dawnside zone but at slightly different L shells see occurrence of EMIC waves but in different frequencies relative to local ion gyrofrequencies. . .
Date: 05/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023827 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023827/full
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Authors: Chiu Y T, Nightingale R W, and Rinaldi M A
Title: Simultaneous Radial and Pitch Angle Diffusion in the Outer Electron Radiation Belt
Abstract: A solution of the bimodal (radial and pitch angle) diffusion equation for the radiation belts is developed with special regard for the requirements of satellite radiation belt data analysis. In this paper, we use this solution to test the bimodal theory of outer electron belt diffusion by confronting it with satellite data. Satellite observations, usually over finite volumes of (L, t) space, are seldom sufficient in space-time duration to cover the relaxation to equilibrium of the entire radiation belt. Since time scales of continuous data coverage are often comparable to that of radiation belt disturbances, it is therefore inappropriate to apply impulsive semi-infinite time response solutions of diffusion theory to interpret data from a finite window of (L, t) space. Observational limitat. . .
Date: 04/1988 Publisher: Journal of Geophysical Research Pages: 2619 - 2632 DOI: 10.1029/JA093iA04p02619 Available at: http://onlinelibrary.wiley.com/doi/10.1029/JA093iA04p02619/abstract
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Authors: Chi P. J., and Le G.
Title: Observations of magnetospheric high-m poloidal waves by ST-5 satellites in low Earth orbit during geomagnetically quiet times
Abstract: The poloidal waves with large azimuthal wavenumbers (m~100) in the magnetosphere are known to be generated by drift or drift bounce resonance with energetic ring current particles, and these waves may play a role in modulating the energetic particles in the inner magnetosphere. When examining the magnetic field data collected by the NASA ST-5 satellites in the low Earth orbit, Le et al. [2011] discovered many wave events with frequencies of 30–200 mHz (in the Pc 2–3 band), and they proposed that these waves should in fact be Doppler-shifted high-m poloidal waves in the magnetosphere with frequencies at only a few mHz (in the Pc 5 band). Using a new method that examines the differences in wave phase detected by the three ST-5 satellites, we confirm that the frequencies in the Earth fram. . .
Date: 05/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021145 Available at: http://doi.wiley.com/10.1002/2015JA021145
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Authors: Chen Yue, Reeves Geoffrey D, Cunningham Gregory S., Redmon Robert J., and Henderson Michael G.
Title: Forecasting and remote sensing outer belt relativistic electrons from low Earth orbit
Abstract: This study demonstrates the feasibility and reliability of using observations from low Earth orbit (LEO) to forecast and nowcast relativistic electrons in the outer radiation belt. We first report a high cross-energy, cross-pitch-angle coherence discovered between the trapped MeV electrons and precipitating approximately hundreds (~100s) of keV electrons—observed by satellites with very different altitudes—with correlation coefficients as high as ≳ 0.85. Based upon the coherence, we then tested the feasibility of applying linear prediction filters to LEO data to predict the arrival of new MeV electrons during geomagnetic storms, as well as their evolving distributions afterward. Reliability of these predictive filters is quantified by the performance efficiency with values as high . . .
Date: 02/2016 Publisher: Geophysical Research Letters Pages: 1031 - 1038 DOI: 10.1002/2015GL067481 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015GL067481/full
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Authors: Chen Yue, Reeves Geoffrey D, Fu Xiangrong, and Henderson Michael
Title: PreMevE: New Predictive Model for Megaelectron-volt Electrons inside Earth's Outer Radiation Belt
Abstract: This work designs a new model called PreMevE to predict storm‐time distributions of relativistic electrons within Earth's outer radiation belt. This model takes advantage of the cross‐energy, ‐L‐shell, and –pitch‐angle coherence associated with wave‐electron resonant interactions, ingests observations from belt boundaries—mainly by NOAA POES in low‐Earth‐orbits (LEOs), and provides high‐fidelity nowcast (multiple‐hour prediction) and forecast (> ~1 day) of MeV electron fluxes over L‐shells between 2.8‐7 through linear prediction filters. PreMevE can not only reliably anticipate incoming enhancements of MeV electrons during storms with at least 1‐day forewarning time, but also accurately specify the evolving event‐specific electron spatial distributions after. . .
Date: 02/2019 Publisher: Space Weather DOI: 10.1029/2018SW002095 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018SW002095
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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: Chen Margaret W., Lemon Colby L., Hecht James, Sazykin Stanislav, Wolf Richard A., et al.
Title: Diffuse Auroral Electron and Ion Precipitation Effects on RCM‐E Comparisons with Satellite Data During the March 17, 2013 Storm
Abstract: Effects of scattering of electrons from whistler chorus waves and of ions due to field line curvature on diffuse precipitating particle fluxes and ionospheric conductance during the large 17 March 2013 storm are examined using the self‐consistent Rice Convection Model Equilibrium (RCM‐E) model. Electrons are found to dominate the diffuse precipitating particle integrated energy flux, with large fluxes from ~21:00 magnetic local time (MLT) eastward to ~11:00 MLT during the storm main phase. Simulated proton and oxygen ion precipitation due to field line curvature scattering is sporadic and localized, occurring where model magnetic field lines are significantly stretched on the night side at equatorial geocentric radial distances r0 ≳8 RE and/or at r0 ~5.5 to 6.5 RE from dusk to midnig. . .
Date: 05/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA026545 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA026545
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Authors: Chen X.-R., Zong Q.-G., Zhou X.-Z., Blake Bernard, Wygant J. R., et al.
Title: Van Allen Probes observation of a 360° phase shift in the flux modulation of injected electrons by ULF waves
Abstract: We present Van Allen Probe observation of drift-resonance interaction between energetic electrons and ultralow frequency (ULF) waves on 29 October 2013. Oscillations in electron flux were observed at the period of ∼450 s, which is also the dominant period of the observed ULF magnetic pulsations. The phase shift of the electron fluxes (∼50 to 150 keV) across the estimated resonant energy (∼104 keV) is ∼360°. This phase relationship is different from the characteristic 180° phase shift as expected from the drift-resonance theory. We speculate that the additional 180° phase difference arises from the inversion of electron phase space density (PSD) gradient, which in turn is caused by the drift motion of the substorm injected electrons. This PSD gradient adjusts the characteristic p. . .
Date: 02/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL071252 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071252/full
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Authors: Chen Yue, Reeves Geoffrey D, Friedel Reiner H W, and Cunningham Gregory S.
Title: Global time-dependent chorus maps from low-Earth-orbit electron precipitation and Van Allen Probes data
Abstract: Substorm injected electrons (several–100 s keV) produce whistler-mode chorus waves that are thought to have a major impact on the radiation belts by causing both energization and loss of relativistic electrons in the outer belt. High-altitude measurements, such as those from the Van Allen Probes, provide detailed wave measurements at a few points in the magnetosphere. But physics-based models of radiation-belt dynamics require knowledge of the global distribution of chorus waves. We demonstrate that time-dependent, global distributions of near-equatorial chorus wave intensities can be inferred from low-Earth-orbit (LEO) measurements of precipitating low-energy electrons. We compare in situ observations of near-equatorial chorus waves with LEO observations of precipitating electrons a. . .
Date: 02/2014 Publisher: Geophysical Research Letters Pages: 755 - 761 DOI: 10.1002/2013GL059181 Available at: http://doi.wiley.com/10.1002/2013GL059181
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Authors: Chen Lunjin, Maldonado Armando, Bortnik Jacob, Thorne Richard M, Li Jinxing, et al.
Title: Nonlinear Bounce Resonances between Magnetosonic Waves and Equatorially Mirroring Electrons
Abstract: Equatorially mirroring energetic electrons pose an interesting scientific problem, since they generally cannot resonate with any known plasma waves and hence cannot be scattered down to lower pitch angles. Observationally it is well known that the fluxof these equatorial particles does not simply continue to build up indefinitely, and so a mechanism must necessarily exist that transports these particles from a equatorial pitch angle of 90 degrees down to lower values. However this mechanism has not been uniquely identified yet. Here, we investigate the mechanism of bounce resonance with equatorial noise (or fast magnetosonic waves). A test particle simulation is used to examine the effects of monochromatic magnetosonic waves on the equatorially mirroring energetic electrons, with a special. . .
Date: 06/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021174 Available at: http://doi.wiley.com/10.1002/2015JA021174
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Authors: Chen Zhe, Chen HongFei, Li YiFan, Xiang HongWen, Yu XiangQian, et al.
Title: Variations of the relativistic electron flux after a magnetospheric compression event
Abstract: On January 21, 2015, a sharp increase of the solar wind dynamic pressure impacted the magnetosphere. The magnetopause moved inward to the region L< 8 without causing a geomagnetic storm. The flux of the relativistic electrons in the outer radiation belt decreased by half during this event based on the observations of the particle radiation monitor (PRM) of the fourth of the China-Brazil Earth Resource Satellites (CBERS-4). The flux remained low for approximately 11 d; it did not recover after a small magnetic storm on January 26 but after a small magnetic storm on February 2. The loss and recovery of the relativistic electrons during this event are investigated using the PRM data, medium- and high-energy electron observations of NOAA-15 and the Van Allen Probes, medium-energy electron obse. . .
Date: 04/2017 Publisher: Science China Technological Sciences Pages: 638 - 647 DOI: 10.1007/s11431-016-9008-3 Available at: https://link.springer.com/article/10.1007/s11431-016-9008-3
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Authors: Chen Y., Friedel R. H. W., Henderson M. G., Claudepierre S. G., Morley S., et al.
Title: REPAD: An Empirical Model of Pitch-angle Distributions for Energetic Electrons in the Earth’s Outer Radiation Belt
Abstract: We have recently conducted a statistical survey on pitch angle distributions of energetic electrons trapped in the Earth's outer radiation belt, and a new empirical model was developed based upon survey results. This model—relativistic electron pitch angle distribution (REPAD)—aims to present statistical pictures of electron equatorial pitch angle distributions, instead of the absolute flux levels, as a function of energy, L shell, magnetic local time, and magnetic activity. To quantify and facilitate this statistical survey, we use Legendre polynomials to fit long-term in situ directional fluxes observed near the magnetic equator from three missions: CRRES, Polar, and LANL-97A. As the first of this kind of model, REPAD covers the whole outer belt region, providing not only the mean an. . .
Date: 03/2014 Publisher: Journal of Geophysical Research Pages: 1693-1708 DOI: 10.1002/2013JA019431 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2013JA019431/full
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Authors: Chen Yue, Friedel Reiner H W, Henderson Michael G., Claudepierre Seth G., Morley Steven K., et al.
Title: REPAD: An empirical model of pitch angle distributions for energetic electrons in the Earth's outer radiation belt
Abstract: We have recently conducted a statistical survey on pitch angle distributions of energetic electrons trapped in the Earth's outer radiation belt, and a new empirical model was developed based upon survey results. This model—relativistic electron pitch angle distribution (REPAD)—aims to present statistical pictures of electron equatorial pitch angle distributions, instead of the absolute flux levels, as a function of energy, L shell, magnetic local time, and magnetic activity. To quantify and facilitate this statistical survey, we use Legendre polynomials to fit long-term in situ directional fluxes observed near the magnetic equator from three missions: CRRES, Polar, and LANL-97A. As the first of this kind of model, REPAD covers the whole outer belt region, providing not only the mean an. . .
Date: 03/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 1693 - 1708 DOI: 10.1002/jgra.v119.310.1002/2013JA019431 Available at: http://doi.wiley.com/10.1002/jgra.v119.3http://doi.wiley.com/10.1002/2013JA019431
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Authors: Chen Yaru, Zhou Qinghua, He Yihua, Yang Chang, Liu Si, et al.
Title: Global occurrences of electrostatic electron cyclotron harmonic waves associated with radiation belt electron distributions
Abstract: Electrostatic electron cyclotron harmonic (ECH) waves can yield diffuse aurora primarily at higher L‐shells by driving efficient precipitation loss of plasma sheet electrons. Here using the Van Allen Probes high resolution data, we examine in detail the global occurrences of ECH waves during the period from October 1, 2012 to June 30, 2017 and find that there are totally 419 events of enhanced ECH waves. The statistical results demonstrate that ECH waves can be present over a broad region of L=4‐6 and 00‐24 MLT, with a higher occurrence in the region of L=5‐6 and 06‐19 MLT. The electron phase space density exhibits a distinct ring distribution (∂f/∂v⊥ >0) with the peak energy around a few keV. Both ECH wave events and the electron ring distributions are closely related and . . .
Date: 04/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL082668 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082668
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Authors: Chen X.-R., Zong Q.-G., Zhou X.-Z., Blake Bernard, Wygant John R., et al.
Title: Van Allen Probes observation of a 360° phase shift in the flux modulation of injected electrons by ULF waves
Abstract: We present Van Allen Probe observation of drift-resonance interaction between energetic electrons and ultra-low frequency (ULF) waves on October 29, 2013. Oscillations in electron flux were observed at the period of ∼450s, which is also the dominant period of the observed ULF magnetic pulsations. The phase shift of the electron fluxes (∼50 to 150 keV) across the estimated resonant energy (∼104 keV) is ∼360°. This phase relationship is different from the characteristic 180° phase shift as expected from the drift-resonance theory. We speculate that the additional 180° phase difference arises from the inversion of electron phase space density (PSD) gradient, which in turn is caused by the drift motion of the substorm injected electrons. This PSD gradient adjusts the characteristic . . .
Date: 12/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL071252 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071252/full
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Authors: Chen Lunjin, Thorne Richard M, Bortnik Jacob, Li Wen, Horne Richard B, et al.
Title: Generation of Unusually Low Frequency Plasmaspheric Hiss
Abstract: It has been reported from Van Allen Probe observations that plasmaspheric hiss intensification in the outer plasmasphere, associated with a substorm injection on Sept 30 2012, occurred with a peak frequency near 100 Hz, well below the typical plasmaspheric hiss frequency range, extending down to ~20 Hz. We examine this event of unusually low frequency plasmaspheric hiss to understand its generation mechanism. Quantitative analysis is performed by simulating wave ray paths via the HOTRAY ray tracing code with measured plasma density and calculating ray path-integrated wave gain evaluated using the measured energetic electron distribution. We demonstrate that the growth rate due to substorm injected electrons is positive but rather weak, leading to small wave gain (~10 dB) during a sin. . .
Date: 08/2014 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL060628 Available at: http://doi.wiley.com/10.1002/2014GL060628
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Authors: Chelpanov Maksim A., Mager Pavel N., Klimushkin Dmitri Yu., Berngardt Oleg I., and Mager Olga V.
Title: Experimental evidence of drift compressional waves in the magnetosphere: an Ekaterinburg coherent decameter radar case study
Abstract: A case study of shortwave radar observations of magnetospheric Pc5 ULF waves (wave periods of 150–600 s) that occurred on 26 December 2014 in the nightside magnetosphere during substorm activity is presented. The radar study of waves in the magnetosphere is based on analysis of scattering from field-aligned irregularities of the ionospheric F layer. Variations of their inline image drift velocity at F layer heights are associated with the wave electric field. Analysis of the observations from the Ekaterinburg (EKB) radar shows that the frequency f of the observed wave depends on the azimuthal wave number m (positive correlation of about 0.90): an increase in frequency from 2.5 to 5 mHz corresponds to increased m number from 20 to 80. Of the known types of waves in the magnetosphere corre. . .
Date: 02/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2015JA022155 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2015JA022155/full
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Authors: Chaston Christopher C., Bonnell J W, Wygant John R., Mozer Forrest, Bale Stuart D., et al.
Title: Observations of kinetic scale field line resonances
Abstract: We identify electromagnetic field variations from the Van Allen Probes which have the properties of Doppler shifted kinetic scale Alfvénic field line resonances. These variations are observed during injections of energetic plasmas into the inner magnetosphere. These waves have scale sizes perpendicular to the magnetic field which are determined to be of the order of an ion gyro-radius (ρi) and less. Cross-spectral analysis of the electric and magnetic fields reveals phase transitions at frequencies correlated with enhancements and depressions in the ratio of the electric and magnetic fields. Modeling shows that these observations are consistent with the excitation of field-line resonances over a broad range of wave numbers perpendicular to the magnetic field (k⊥) extending to k⊥ρi. . .
Date: 01/2014 Publisher: Geophysical Research Letters Pages: 209 - 215 DOI: 10.1002/2013GL058507 Available at: http://doi.wiley.com/10.1002/2013GL058507
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Authors: Chaston C. C., Bonnell J. W., Wygant J R, Reeves G D, Baker D N, et al.
Title: Radiation belt “dropouts” and drift-bounce resonances in broadband electromagnetic waves
Abstract: Observations during the main phase of geomagnetic storms reveal an anti-correlation between the occurrence of broadband low frequency electromagnetic waves and outer radiation belt electron flux. We show that the drift-bounce motion of electrons in the magnetic field of these waves leads to rapid electron transport. For observed spectral energy densities it is demonstrated that the wave magnetic field can drive radial diffusion via drift-bounce resonance on timescales less than a drift orbit. This process may provide outward transport sufficient to account for electron “dropouts” during storm main phase and more generally modulate the outer radiation belt during geomagnetic storms.
Date: 02/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL076362 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL076362/full
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Authors: Chaston C. C., Bonnell J. W., Wygant J R, Kletzing C A, Reeves G D, et al.
Title: Extreme ionospheric ion energization and electron heating in Alfvén waves in the storm-time inner magnetosphere
Abstract: We report measurements of energized outflowing/bouncing ionospheric ions and heated electrons in the inner magnetosphere during a geomagnetic storm. The ions arrive in the equatorial plane with pitch angles that increase with energy over a range from tens of eV to > 50 keV while the electrons are field-aligned up to ~1 keV. These particle distributions are observed during intervals of broadband low frequency electromagnetic field fluctuations consistent with a Doppler-shifted spectrum of kinetic Alfvén waves and kinetic field-line resonances. The fluctuations extend from L≈3 out to the apogee of the Van Allen Probes spacecraft at L≈6.5. They thereby span most of the L-shell range occupied by the ring current. These measurements suggest a model for ionospheric ion outflow and energizat. . .
Date: 12/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL066674 Available at: http://doi.wiley.com/10.1002/2015GL066674http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015GL066674
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Authors: Chaston C. C., Bonnell J. W., Halford A J, Reeves G D, Baker D N, et al.
Title: Pitch Angle Scattering and Loss of Radiation Belt Electrons in Broadband Electromagnetic Waves
Abstract: A magnetic conjunction between Van Allen Probes spacecraft and the Balloon Array for Radiation‐belt Relativistic Electron Losses (BARREL) reveals the simultaneous occurrence of broadband Alfvénic fluctuations and multi‐timescale modulation of enhanced atmospheric X‐ray bremsstrahlung emission. The properties of the Alfvénic fluctuations are used to build a model for pitch angle scattering in the outer radiation belt on electron gyro‐radii scale field structures. It is shown that this scattering may lead to the transport of electrons into the loss cone over an energy range from hundreds of keV to multi‐MeV on diffusive timescales on the order of hours. This process may account for modulation of atmospheric X‐ray fluxes observed from balloons and constitute a significant loss p. . .
Date: 09/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079527 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL079527
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Authors: Chaston C. C., Bonnell J. W., Reeves G D, and Skoug R M
Title: Driving ionospheric outflows and magnetospheric O + energy density with Alfvén waves
Abstract: We show how dispersive Alfvén waves observed in the inner magnetosphere during geomagnetic storms can extract O+ ions from the topside ionosphere and accelerate these ions to energies exceeding 50 keV in the equatorial plane. This occurs through wave trapping, a variant of “shock” surfing, and stochastic ion acceleration. These processes in combination with the mirror force drive field-aligned beams of outflowing ionospheric ions into the equatorial plane that evolve to provide energetic O+ distributions trapped near the equator. These waves also accelerate preexisting/injected ion populations on the same field lines. We show that the action of dispersive Alfvén waves over several minutes may drive order of magnitude increases in O+ ion pressure to make substantial contributions to. . .
Date: 05/2016 Publisher: Geophysical Research Letters Pages: 4825 - 4833 DOI: 10.1002/2016GL069008 Available at: http://doi.wiley.com/10.1002/2016GL069008
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Authors: Chaston C. C., Bonnell J. W., Wygant J R, Reeves G D, Baker D N, et al.
Title: Radial transport of radiation belt electrons in kinetic field-line resonances
Abstract: A representative case study from the Van Allen Probes during a geomagnetic storm recovery phase reveals enhanced electron fluxes at intermediate pitch angles over energies from ~100 keV to 5 MeV coincident with broadband low frequency electromagnetic waves. The statistical properties of these waves are used to build a model for radial diffusion via drift-bounce resonances in kinetic Alfvén eigenmodes/kinetic field-line resonances. Estimated diffusion coefficients indicate timescales for radial transport of the order of hours in storm-time events at energies from <100 keV to MeVs over equatorial pitch angles from the edge of the loss cone to nearly perpendicular to the geomagnetic field. The correlation of kinetic resonances with electron depletions and enhancements during storm main phase. . .
Date: 07/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074587 Available at: onlinelibrary.wiley.com/doi/10.1002/2017GL074587/full
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Authors: Chaston C. C., Bonnell J. W., Kletzing C A, Hospodarsky G B, Wygant J R, et al.
Title: Broadband low frequency electromagnetic waves in the inner magnetosphere
Abstract: A prominent yet largely unrecognized feature of the inner magnetosphere associated with particle injections, and more generally geomagnetic storms, is the occurrence of broadband electromagnetic field fluctuations over spacecraft frame frequencies (fsc) extending from effectively zero to fsc ≳ 100 Hz. Using observations from the Van Allen Probes we show that these waves most commonly occur pre-midnight but are observed over a range of local times extending into the dayside magnetosphere. We find that the variation of magnetic spectral energy density with fsc obeys inline image over several decades with a spectral break-point at fb ≈1 Hz. The values for α are log normally distributed with α = 1.9 ± 0.6 for fsc < fb andα = 2.9 ± 0.6 for fsc > fb. A is . . .
Date: 09/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021690 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015JA021690/abstract
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Authors: Cattell C., Breneman A., Colpitts C., Dombeck J., Thaller S., et al.
Title: Dayside response of the magnetosphere to a small shock compression: Van Allen Probes, Magnetospheric MultiScale, and GOES-13
Abstract: Observations from Magnetospheric MultiScale (~8 Re) and Van Allen Probes (~5 and 4 Re) show that the initial dayside response to a small interplanetary shock is a double-peaked dawnward electric field, which is distinctly different from the usual bipolar (dawnward and then duskward) signature reported for large shocks. The associated ExB flow is radially inward. The shock compressed the magnetopause to inside 8 Re, as observed by MMS, with a speed that is comparable to the ExB flow. The magnetopause speed and the ExB speeds were significantly less than the propagation speed of the pulse from MMS to the Van Allen Probes and GOES-13, which is consistent with the MHD fast mode. There were increased fluxes of energetic electrons up to several MeV. Signatures of drift echoes and response to ULF. . .
Date: 08/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL074895 Available at: onlinelibrary.wiley.com/doi/10.1002/2017GL074895/full
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Authors: Cattell C. A., Breneman A. W., Thaller S. A., Wygant J R, Kletzing C A, et al.
Title: Van Allen Probes observations of unusually low frequency whistler mode waves observed in association with moderate magnetic storms: Statistical study
Abstract: We show the first evidence for locally excited chorus at frequencies below 0.1 fce (electron cyclotron frequency) in the outer radiation belt. A statistical study of chorus during geomagnetic storms observed by the Van Allen Probes found that frequencies are often dramatically lower than expected. The frequency at peak power suddenly stops tracking the equatorial 0.5 fce and f/fce decreases rapidly, often to frequencies well below 0.1 fce (in situ and mapped to equator). These very low frequency waves are observed both when the satellites are close to the equatorial plane and at higher magnetic latitudes. Poynting flux is consistent with generation at the equator. Wave amplitudes can be up to 20 to 40 mV/m and 2 to 4 nT. We conclude that conditions during moderate to large storms. . .
Date: 09/2015 Publisher: Geophysical Research Letters Pages: 7273 - 7281 DOI: 10.1002/2015GL065565 Available at: http://doi.wiley.com/10.1002/2015GL065565http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2F2015GL065565
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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: Capannolo L., Li W, Ma Q, Zhang X.-J., Redmon R. J., et al.
Title: Understanding the Driver of Energetic Electron Precipitation Using Coordinated Multisatellite Measurements
Abstract: Magnetospheric plasma waves play a significant role in ring current and radiation belt dynamics, leading to pitch angle scattering loss and/or stochastic acceleration of the particles. During a non‐storm time dropout event on 24 September 2013, intense electromagnetic ion cyclotron (EMIC) waves were detected by Van Allen Probe A (Radiation Belt Storm Probes‐A). We quantitatively analyze a conjunction event when Van Allen Probe A was located approximately along the same magnetic field line as MetOp‐01, which detected simultaneous precipitation of >30 keV protons and energetic electrons over an unexpectedly broad energy range (>~30 keV). Multipoint observations together with quasi‐linear theory provide direct evidence that the observed electron precipitation at higher energy (>~700 k. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078604 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078604
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Authors: Cao Xing, Ni Binbin, Summers Danny, Zou Zhengyang, Fu Song, et al.
Title: Bounce resonance scattering of radiation belt electrons by low-frequency hiss: Comparison with cyclotron and Landau resonances
Abstract: Bounce-resonant interactions with magnetospheric waves have been proposed as important contributing mechanisms for scattering near-equatorially mirroring electrons by violating the second adiabatic invariant associated with the electron bounce motion along a geomagnetic field line. This study demonstrates that low-frequency plasmaspheric hiss with significant wave power below 100 Hz can bounce-resonate efficiently with radiation belt electrons. By performing quantitative calculations of pitch-angle scattering rates, we show that low-frequency hiss induced bounce-resonant scattering of electrons has a strong dependence on equatorial pitch-angle αeq. For electrons with αeq close to 90°, the timescale associated with bounce resonance scattering can be comparable to or even less than 1 hour. . .
Date: 09/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL075104 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL075104/full
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Authors: Cao Xing, Ni Binbin, Summers Danny, Shprits Yuri Y, Gu Xudong, et al.
Title: Sensitivity of EMIC Wave-Driven Scattering Loss of Ring Current Protons to Wave Normal Angle Distribution
Abstract: Electromagnetic ion cyclotron waves have long been recognized to play a crucial role in the dynamic loss of ring current protons. While the field‐aligned propagation approximation of electromagnetic ion cyclotron waves was widely used to quantify the scattering loss of ring current protons, in this study, we find that the wave normal distribution strongly affects the pitch angle scattering efficiency of protons. Increase of peak normal angle or angular width can considerably reduce the scattering rates of ≤10 keV protons. For >10 keV protons, the field‐aligned propagation approximation results in a pronounced underestimate of the scattering of intermediate equatorial pitch angle protons and overestimates the scattering of high equatorial pitch angle protons by orders of magnitude. Ou. . .
Date: 01/2019 Publisher: Geophysical Research Letters Pages: 590 - 598 DOI: 10.1029/2018GL081550 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL081550
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Authors: Califf S., Li X., Zhao H., Kellerman A., Sarris T. E., et al.
Title: The role of the convection electric field in filling the slot region between the inner and outer radiation belts
Abstract: The Van Allen Probes have reported frequent flux enhancements of 100s keV electrons in the slot region, with lower energy electrons exhibiting more dynamic behavior at lower L shells. Also, in situ electric field measurements from the Combined Release and Radiation Effects Satellite, Time History of Events and Macroscale Interactions during Substorms (THEMIS), and the Van Allen Probes have provided evidence for large-scale electric fields at low L shells during active times. We study an event on 19 February 2014 where hundreds of keV electron fluxes were enhanced by orders of magnitude in the slot region and electric fields of 1–2 mV/m were observed below L = 3. Using a 2-D guiding center particle tracer and a simple large-scale convection electric field model, we demonstrate that . . .
Date: 02/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023657 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023657/full
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Authors: Califf S., Li X, Blum L., Jaynes A., Schiller Q., et al.
Title: THEMIS measurements of quasi-static electric fields in the inner magnetosphere
Abstract: We use four years of THEMIS double-probe measurements to offer, for the first time, a complete picture of the dawn-dusk electric field covering all local times and radial distances in the inner magnetosphere based on in situ equatorial observations. This study is motivated by the results from the CRRES mission, which revealed a local maximum in the electric field developing near Earth during storm times, rather than the expected enhancement at higher L shells that is shielded near Earth as suggested by the Volland-Stern model. The CRRES observations were limited to the dusk side, while THEMIS provides complete local time coverage. We show strong agreement with the CRRES results on the dusk side, with a local maximum near L =4 for moderate levels of geomagnetic activity and evidence of stro. . .
Date: 10/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020360 Available at: http://doi.wiley.com/10.1002/2014JA020360
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