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K
Authors: Kurita S., Miyoshi Y, Shiokawa K., Higashio N., Mitani T., et al.
Title: Rapid loss of relativistic electrons by EMIC waves in the outer radiation belt observed by Arase, Van Allen Probes, and the PWING ground stations
Abstract: There has been increasing evidence for pitch angle scattering of relativistic electrons by electromagnetic ion cyclotron (EMIC) waves. Theoretical studies have predicted that the loss time scale of MeV electrons by EMIC waves can be very fast, suggesting that MeV electron fluxes rapidly decrease in association with the EMIC wave activity. This study reports on a unique event of MeV electron loss induced by EMIC waves based on Arase, Van Allen Probes, and ground‐based network observations. Arase observed a signature of MeV electron loss by EMIC waves, and the satellite and ground‐based observations constrained spatial‐temporal variations of the EMIC wave activity during the loss event. Multi‐satellite observation of MeV electron fluxes showed that ~2.5 MeV electron fluxes substantia. . .
Date: 11/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080262 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080262
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Authors: Kubota Yuko, Omura Yoshiharu, Kletzing Craig, and Reeves Geoff
Title: Generation process of large-amplitude upper band chorus emissions observed by Van Allen Probes
Abstract: We analyze large‐amplitude upper‐band chorus emissions measured near the magnetic equator by the EMFISIS (Electric and Magnetic Field Instrument Suite and Integrated Science) instrument package onboard the Van Allen Probes. In setting up the parameters of source electrons exciting the emissions based on theoretical analyses and observational results measured by the HOPE (Helium Oxygen Proton Electron) instrument, we calculate threshold and optimum amplitudes with the nonlinear wave growth theory. We find that the optimum amplitude is larger than the threshold amplitude obtained in the frequency range of the chorus emissions and that the wave amplitudes grow between the threshold and optimum amplitudes. In the frame of the wave growth process, the nonlinear growth rates are much greater. . .
Date: 04/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2017JA024782 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017JA024782
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Authors: Kim Jin-Hee, Lee Dae-Young, Cho Jung-Hee, Shin Dae-Kyu, Kim Kyung-Chan, et al.
Title: A prediction model for the global distribution of whistler chorus wave amplitude developed separately for two latitudinal zones
Abstract: Whistler mode chorus waves are considered to play a central role in accelerating and scattering electrons in the outer radiation belt. While in situ measurements are usually limited to the trajectories of a small number of satellites, rigorous theoretical modeling requires a global distribution of chorus wave characteristics. In the present work, by using a large database of chorus wave observations made on the Time History of Events and Macroscale Interactions during Substorms satellites for about 5 years, we develop prediction models for a global distribution of chorus amplitudes. The development is based on two main components: (a) the temporal dependence of average chorus amplitudes determined by correlating with the preceding solar wind and geomagnetic conditions as represented by t. . .
Date: 04/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020900 Available at: http://doi.wiley.com/10.1002/2014JA020900
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Authors: Khoo Leng Ying, Li Xinlin, Zhao Hong, Sarris Theodore, Xiang Zheng, et al.
Title: On the Initial Enhancement of Energetic Electrons and the Innermost Plasmapause Locations: CME-Driven Storm Periods
Abstract: Using Van Allen Probes’ observations and established plasmapause location (Lpp) models, we investigate the relationship between the location of the initial enhancement (IE) of energetic electrons and the innermost (among all magnetic local time sectors) Lpp over five intense storm periods. Our study reveals that the IE events for 30 keV to 2MeV electrons always occurred outside of the innermost Lpp. On average, the inner extent of the IE events (LIE) for <800 keV electrons was closer to the innermost Lpp when compared to the LIE for >800 keV electrons that was found consistently at ~1.5 RE outside of the innermost Lpp. The IE of 10s keV electrons was observed before the IE of 100s keV electrons, and the IE of >800 keV electrons was observed on average 12.6±2.3 hours after the occurrence. . .
Date: 10/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026074 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026074
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Authors: Kessel Mona
Title: Things we don't yet understand about solar driving of the radiation belts.
Abstract: This commentary explores how close we are to predicting the behavior of the radiations belts - the primary science objective of NASA's Van Allen Probes mission. Starting with what we know or think we know about competing sources, enhancement, transport, and loss, I walk through recent papers that have improved our understanding and then focus on flux dropouts as one particular yardstick of success. I mention a new paradigm for electrons and the importance of reliably matching models and observations for different solar inputs. Although the case for prediction remains a work in progress, there are encouraging signs of progress.
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022472 Available at: http://doi.wiley.com/10.1002/2016JA022472
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Authors: Hwang Junga, and Yoon Peter H.
Title: High-frequency thermal fluctuations and instabilities in the radiation belt environment
Abstract: This paper overviews the electrostatic and electromagnetic theories of spontaneous emission in magnetized plasma as they relate to measured electric and magnetic field fluctuations in quiet time radiation belt and ring current region. The pervasively detected high‐frequency fluctuations in the upper‐hybrid frequency range as well as the background low‐frequency range spectral profile in the whistler mode range are explained within the context of the spontaneous emission theory. The quasilinear calculation of loss‐cone instability is also carried out in order to validate the assumption of spontaneous emission model. It is shown that the saturated wave amplitudes associated with the upper‐hybrid and multiple‐harmonic cyclotron instability are quite low, indicating that the theore. . .
Date: 10/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025643 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025643
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Authors: Hwang J., Choi E.-J., Park J.-S., Fok M.-C., Lee D.-Y., et al.
Title: Comprehensive analysis of the flux dropout during 7-8 November 2008 storm using multi-satellites observations and RBE model
Abstract: We investigate an electron flux dropout during a weak storm on 7–8 November 2008, with Dst minimum value being −37 nT. During this period, two clear dropouts were observed on GOES 11 > 2 MeV electrons. We also find a simultaneous dropout in the subrelativistic electrons recorded by Time History of Events and Macroscale Interactions during Substorms probes in the outer radiation belt. Using the Radiation Belt Environment model, we try to reproduce the observed dropout features in both relativistic and subrelativistic electrons. We found that there are local time dependences in the dropout for both observation and simulation in subrelativistic electrons: (1) particle loss begins from nightside and propagates into dayside and (2) resupply starts from near dawn magnetic local time . . .
Date: 05/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021085 Available at: http://doi.wiley.com/10.1002/2015JA021085
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Authors: Hudson Mary, Jaynes Allison, Kress Brian, Li Zhao, Patel Maulik, et al.
Title: Simulated prompt acceleration of multi-MeV electrons by the 17 March 2015 interplanetary shock
Abstract: Prompt enhancement of relativistic electron flux at L = 3−5 has been reported from Van Allen Probes Relativistic Electron Proton Telescope (REPT) measurements associated with the 17 March 2015 interplanetary shock compression of the dayside magnetosphere. Acceleration by ∼ 1 MeV is inferred on less than a drift time scale as seen in prior shock compression events, which launch a magetosonic azimuthal electric field impulse tailward. This impulse propagates from the dayside around the flanks accelerating electrons in drift resonance at the dusk flank. Such longitudinally localized acceleration events produce a drift echo signature which was seen at >1 MeV energy on both Van Allen Probe spacecraft, with sustained observations by Probe B outbound at L = 5 at 2100 MLT at the time of impuls. . .
Date: 09/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024445 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024445/full
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Authors: He Yihua, Xiao Fuliang, Su Zhenpeng, Zheng Huinan, Yang Chang, et al.
Title: Generation of lower L -shell dayside chorus by energetic electrons from the plasmasheet
Abstract: Currently, the generation mechanism for the lower L‐shell dayside chorus has still remained an open question. Here, we report two storm events: 06‐07 March 2016 and 20‐21 January 2016, when Van Allen Probes observed enhanced dayside chorus with lower and higher wave normal angles (the angles between the wave vector and the geomagnetic field) in the region of L = 3.5‐6.3 and MLT = 5.6‐13.5. Hot and energetic (∼ 1‐100 keV) electrons displayed enhancements in fluxes and anisotropy when they were injected from the plasmasheet and drifted from midnight through dawn toward the dayside. Calculations of chorus local growth rates under different waves normal angles show that the upper cutoff and peak wave frequencies display similar patterns to the observations. Chorus growth rates ma. . .
Date: 09/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2017JA024889 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017JA024889
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Authors: Glauert Sarah A, Horne Richard B, and Meredith Nigel P
Title: Simulating the Earth's radiation belts: Internal acceleration and continuous losses to the magnetopause
Abstract: In the Earth's radiation belts the flux of relativistic electrons is highly variable, sometimes changing by orders of magnitude within a few hours. Since energetic electrons can damage satellites it is important to understand the processes driving these changes and, ultimately, to develop forecasts of the energetic electron population. One approach is to use three-dimensional diffusion models, based on a Fokker-Planck equation. Here we describe a model where the phase-space density is set to zero at the outer L∗ boundary, simulating losses to the magnetopause, using recently published chorus diffusion coefficients for 1.5≤L∗≤10. The value of the phase-space density on the minimum-energy boundary is determined from a recently published, solar wind-dependent, statistical model. Our s. . .
Date: 09/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: 7444 - 7463 DOI: 10.1002/jgra.v119.910.1002/2014JA020092 Available at: http://doi.wiley.com/10.1002/jgra.v119.9http://doi.wiley.com/10.1002/2014JA020092
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Authors: Gao Zhonglei, Su Zhenpeng, Xiao Fuliang, Summers Danny, Liu Nigang, et al.
Title: Nonlinear coupling between whistler-mode chorus and electron cyclotron harmonic waves in the magnetosphere
Abstract: Electromagnetic whistler‐mode chorus and electrostatic electron cyclotron harmonic (ECH) waves can contribute significantly to auroral electron precipitation and radiation belt electron acceleration. In the past, linear and nonlinear wave‐particle interactions have been proposed to explain the occurrences of these magnetospheric waves. By analyzing Van Allen Probes data, we present here the first evidence for nonlinear coupling between chorus and ECH waves. The sum‐frequency and difference‐frequency interactions produced the ECH sidebands with discrete frequency sweeping structures exactly corresponding to the chorus rising tones. The newly‐generated weak sidebands did not satisfy the original electrostatic wave dispersion relation. After the generation of chorus and normal ECH w. . .
Date: 11/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080635 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080635
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F
Authors: Foster J. C., Erickson P. J., Omura Y., Baker D. N., Kletzing C. A., et al.
Title: Van Allen Probes observations of prompt MeV radiation belt electron acceleration in nonlinear interactions with VLF chorus
Abstract: Prompt recovery of MeV (millions of electron Volts) electron populations in the poststorm core of the outer terrestrial radiation belt involves local acceleration of a seed population of energetic electrons in interactions with VLF chorus waves. Electron interactions during the generation of VLF rising tones are strongly nonlinear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant nonadiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by Van Allen Probes, we investigate the efficiency of nonlinear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy of hundreds of keV to 3 MeV can be a. . .
Date: 01/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023429 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023429
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Authors: Foster J. C., Erickson P. J., Omura Y., Baker D N, Kletzing C A, et al.
Title: Van Allen Probes Observations of Prompt MeV Radiation Belt Electron Acceleration in Non-Linear Interactions with VLF Chorus
Abstract: Prompt recovery of MeV electron populations in the post-storm core of the outer terrestrial radiation belt involves local acceleration of a seed population of energetic electrons in interactions with VLF chorus waves. Electron interactions during the generation of VLF rising tones are strongly non-linear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant non-adiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by Van Allen Probes, we investigate the efficiency of non-linear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy 100s keV - 3 MeV can be accelerated by 50 keV - 200 keV in re. . .
Date: 12/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023429 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023429/full
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Authors: Engel M. A., Kress B T, Hudson M K, and Selesnick R. S.
Title: Comparison of Van Allen Probes radiation belt proton data with test particle simulation for the 17 March 2015 storm
Abstract: The loss of protons in the outer part of the inner radiation belt (L = 2 to 3) during the 17 March 2015 geomagnetic storm was investigated using test particle simulations that follow full Lorentz trajectories with both magnetic and electric fields calculated from an empirical model. The simulation results presented here are compared with proton pitch angle measurements from the Van Allen Probe satellites Relativistic Electron Proton Telescope (REPT) instrument before and after the coronal mass ejection-shock-driven storm of 17–18 March 2015, with minimum Dst =− 223 nT, the strongest storm of Solar Cycle 24, for four different energy ranges with 30, 38, 50, and 66 MeV mean energies. Two simulations have been run, one with an inductive electric field and one without. All four energy chan. . .
Date: 11/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023333 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016JA023333/full
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Authors: Dai Guyue, Su Zhenpeng, Liu Nigang, Wang Bin, Zheng Huinan, et al.
Title: Quenching of Equatorial Magnetosonic Waves by Substorm Proton Injections
Abstract: Near equatorial (fast) magnetosonic waves, characterized by high magnetic compressibility, are whistler‐mode emissions destabilized by proton shell/ring distributions. In the past, substorm proton injections are widely known to intensify magnetosonic waves in the inner magnetosphere. Here we report the unexpected observations by the Van Allen Probes of the magnetosonic wave quenching associated with the substorm proton injections under both high‐ and low‐density conditions. The enhanced proton thermal pressure distorted the background magnetic field configuration and the cold plasma density distribution. The reduced phase velocities locally allowed the weak growth or even damping of magnetosonic waves. Meanwhile, the spatially irregularly varying refractive indices might suppress the. . .
Date: 05/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL082944 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082944
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C
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: 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: 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, 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: 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 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: 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: Boyd A.J., Turner D.L., Reeves G.D., Spence H.E., Baker D.N., et al.
Title: What Causes Radiation Belt Enhancements: A Survey of the Van Allen Probes Era
Abstract: We survey radiation belt enhancement events during the Van Allen Probes era to determine what mechanism is the dominant cause of enhancements and where it is most effective. Two primary mechanisms have been proposed: (1) betatron/Fermi acceleration due to the Earthward radial transport of electrons which produces monotonic gradients in phase space density (PSD) and (2) “local acceleration" due to gyro/Landau resonant interaction with electromagnetic waves which produces radially localized, growing peaks in PSD. To differentiate between these processes, we examine radial profiles of PSD in adiabatic coordinates using data from the Van Allen Probes and THEMIS satellites for 80 outer belt enhancement events from October 2012‐April 2017 This study shows that local acceleration is the domin. . .
Date: 05/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL077699 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL077699
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Authors: Boyd A.J., Spence H.E., Huang C.-L., Reeves G D, Baker D N, et al.
Title: Statistical Properties of the Radiation Belt Seed Population
Abstract: We present a statistical analysis of phase space density data from the first 26 months of the Van Allen Probes mission. In particular we investigate the relationship between the 10s-100s keV seed electrons and >1 MeV core radiation belt electron population. Using a cross correlation analysis, we find that the seed and core populations are well correlated with a coefficient of ≈ 0.73 with a time lag of 10-15 hours. We present evidence of a seed population threshold that is necessary for subsequent acceleration. The depth of penetration of the seed population determines the inner boundary of the acceleration process. However, we show that an enhanced seed population alone is not enough to produce acceleration in the higher energies, implying that the seed population of 100s of keV electron. . .
Date: 07/2016 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA022652 Available at: http://doi.wiley.com/10.1002/2016JA022652
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