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2018
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: 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: 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: Yu Xiongdong, Yuan Zhigang, Huang Shiyong, Yao Fei, Wang Dedong, et al.
Title: Excitation of O + Band EMIC Waves Through H + Ring Velocity Distributions: Van Allen Probe Observations
Abstract: A typical case of electromagnetic ion cyclotron (EMIC) emissions with both He+ band and O+ band waves was observed by Van Allen Probe A on 14 July 2014. These emissions occurred in the morning sector on the equator inside the plasmasphere, in which region O+ band EMIC waves prefer to appear. Through property analysis of these emissions, it is found that the He+ band EMIC waves are linearly polarized and propagating quasi-parallelly along the background magnetic field, while the O+ band ones are of linear and left-hand polarization and propagating obliquely with respect to the background magnetic field. Using the in situ observations of plasma environment and particle data, excitation of these O+ band EMIC waves has been investigated with the linear growth theory. The calculated linear grow. . .
Date: 02/2018 Publisher: Geophysical Research Letters Pages: 1271 - 1276 DOI: 10.1002/grl.v45.310.1002/2018GL077109 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2018GL077109/full
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Authors: Jaynes A. N., Ali A. F., Elkington S R, Malaspina D. M., Baker D N, et al.
Title: Fast diffusion of ultra-relativistic electrons in the outer radiation belt: 17 March 2015 storm event
Abstract: Inward radial diffusion driven by ULF waves has long been known to be capable of accelerating radiation belt electrons to very high energies within the heart of the belts, but more recent work has shown that radial diffusion values can be highly event‐specific and mean values or empirical models may not capture the full significance of radial diffusion to acceleration events. Here we present an event of fast inward radial diffusion, occurring during a period following the geomagnetic storm of 17 March 2015. Ultra‐relativistic electrons up to ∼8 MeV are accelerated in the absence of intense higher‐frequency plasma waves, indicating an acceleration event in the core of the outer belt driven primarily or entirely by ULF wave‐driven diffusion. We examine this fast diffusion rate alon. . .
Date: 09/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079786 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL079786
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Authors: Min Kyungguk, Liu Kaijun, Wang Xueyi, Chen Lunjin, and Denton Richard E
Title: Fast Magnetosonic Waves Observed by Van Allen Probes: Testing Local Wave Excitation Mechanism
Abstract: Linear Vlasov theory and particle-in-cell (PIC) simulations for electromagnetic fluctuations in a homogeneous, magnetized, and collisionless plasma are used to investigate a fast magnetosonic wave event observed by the Van Allen Probes. The fluctuating magnetic field observed exhibits a series of spectral peaks at harmonics of the proton cyclotron frequency Ωp and has a dominant compressional component, which can be classified as fast magnetosonic waves. Furthermore, the simultaneously observed proton phase space density exhibits positive slopes in the perpendicular velocity space, ∂fp/∂v⊥>0, which can be a source for these waves. Linear theory analyses and PIC simulations use plasma and field parameters measured in situ except that the modeled proton distribution is modified to hav. . .
Date: 01/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024867 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024867/full
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Authors: Nakamura S., Omura Y., and Summers D.
Title: Fine structure of whistler-mode hiss in plasmaspheric plumes observed by the Van Allen Probes
Abstract: We survey 3 years (2013‐2015) of data from the Van Allen Probes related to plasmaspheric plume crossing events. We detect 194 plume crossing events, and we find that 97% of the plumes are accompanied by VLF hiss emissions. The plumes are mainly detected on the duskside or dayside. Careful examination of the hiss spectra reveals that all hiss emissions consist of obvious fine structure. Application of a band pass filter reveals that the fine structure is consistent with the occurrence of discrete wave packets. The hiss data display high coherency. The events are classified by location. Dusk side hiss and night side hiss tend to have extremely high polarization with no chorus at the high‐frequency end of the dynamic spectrum. The dusk side hiss has a distinct upper frequency limit. On th. . .
Date: 10/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025803 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025803
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Authors: Maurer R H, Goldsten J O, Butler M. H., and Fretz K.
Title: Five Year Results from the Engineering Radiation Monitor (ERM) and Solar Cell Monitor on the Van Allen Probes Mission
Abstract: The Engineering Radiation Monitor (ERM) measures dose, dose rate and charging currents on the Van Allen Probes mission to study the dynamics of Earth's Van Allen radiation belts. Over five years, results from this monitor show a variation in dose rates with time, a correlation between the dosimeter and charging current data and a comparison of cumulative dose to pre‐launch modeling. Solar cell degradation monitor patches track the decrease in solar array output as displacement damage accumulates. The Solar Cell Monitor shows ~33% cumulative degradation in maximum power after 5.1 years of the mission. The desire to extend the mission to ~2500 days from 800 days created increased requirements for the ionizing radiation hardness of spacecraft and science instrument electronics. We describe . . .
Date: 09/2018 Publisher: Space Weather DOI: 10.1029/2018SW001910 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018SW001910
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Authors: Gamayunov Konstantin V., Min Kyungguk, Saikin Anthony A., and Rassoul Hamid
Title: Generation of EMIC Waves Observed by Van Allen Probes at Low L Shells
Abstract: Observation of linearly polarized He+‐band electromagnetic ion cyclotron (EMIC) waves at low L shells is a new, and quite unexpected, result from the Van Allen Probes mission. Here we analyze the two EMIC wave events observed by Van Allen Probes at low L shells and put forward a new‐generation mechanism for the low‐L EMIC waves. Both events were observed at L ∼ 3 but one of them has a discrete spectrum near the O+ gyrofrequency and its second harmonic, whereas the second event has a broad spectrum between the O+ gyrofrequency and its second harmonic. For both events, the major conclusions of our analysis can be summarized as follows. (1) Only O+ causes EMIC wave generation, and instability is driven by the positive derivatives of distribution functions over perpendicular component . . .
Date: 10/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025629 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025629
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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: 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: Yuan Zhigang, Ouyang Zhihai, Yu Xiongdong, Huang Shiyong, Yao Fei, et al.
Title: Global distribution of proton rings and associated magnetosonic wave instability in the inner magnetosphere
Abstract: Using the Van Allen Probe A observations, we obtained the global distribution of proton rings and calculated the linear wave growth rate of fast magnetosonic (MS) waves in the region L ~ 3‐6. Our statistical and calculated results demonstrate that MS waves can be locally excited on the dayside outside the plasmapause, as well as in the dusk sector inside the plasmapause. The frequency range of unstable MS waves is strongly modulated by the ratio of the proton ring velocity (Vr) to the local Alfvén speed (VA). High harmonic MS waves (ω>20ΩH+) can be excited outside the plasmapause where Vr/VA<1 while low harmonic MS waves (ω<10ΩH+) with frequencies less than ~30 Hz are found to be excited both outside and inside the plasmapause where 1Date: 09/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079999 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL079999
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Authors: Meredith Nigel P, Horne Richard B, Kersten Tobias, Li Wen, Bortnik Jacob, et al.
Title: Global model of plasmaspheric hiss from multiple satellite observations
Abstract: We present a global model of plasmaspheric hiss, using data from eight satellites, extending the coverage and improving the statistics of existing models. We use geomagnetic activity dependent templates to separate plasmaspheric hiss from chorus. In the region 22‐14 MLT the boundary between plasmaspheric hiss and chorus moves to lower L∗ values with increasing geomagnetic activity. The average wave intensity of plasmaspheric hiss is largest on the dayside and increases with increasing geomagnetic activity from midnight through dawn to dusk. Plasmaspheric hiss is most intense and spatially extended in the 200‐500 Hz frequency band during active conditions, 400 Date: 05/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025226 Available at: http://doi.wiley.com/10.1029/2018JA025226http://onlinelibrary.wiley.com/wol1/doi/10.1029/2018JA025226/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1029%2F2018JA025226
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Authors: Murphy Kyle R., Watt C. E. J., Mann Ian R., Rae Jonathan, Sibeck David G., et al.
Title: The global statistical response of the outer radiation belt during geomagnetic storms
Abstract: Using the total radiation belt electron content calculated from Van Allen Probe phase space density (PSD), the time‐dependent and global response of the outer radiation belt during storms is statistically studied. Using PSD reduces the impacts of adiabatic changes in the main phase, allowing a separation of adiabatic and non‐adiabatic effects, and revealing a clear modality and repeatable sequence of events in storm‐time radiation belt electron dynamics. This sequence exhibits an important first adiabatic invariant (μ) dependent behaviour in the seed (150 MeV/G), relativistic (1000 MeV/G), and ultra‐relativistic (4000 MeV/G) populations. The outer radiation belt statistically shows an initial phase dominated by loss followed by a second phase of rapid acceleration, whilst the seed. . .
Date: 04/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL076674 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2017GL076674
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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: Shi R., Mourenas D., Artemyev A., Li W, and Ma Q
Title: Highly Oblique Lower-Band Chorus Statistics: Dependencies of Wave Power on Refractive Index and Geomagnetic Activity
Abstract: We use 3 years of Van Allen Probes observations of highly oblique lower‐band chorus waves at low latitudes over L = 4–6 to provide a comprehensive statistics of the distribution of their magnetic and electric powers and full energy density as a function of wave refractive index N, L shell, and geomagnetic activity AE. We use the refractive index calculated either in the cold plasma approximation or in the quasi‐electrostatic (hot plasma) approximation and either observed wave electric fields or corrected wave electric fields accounting for the formation of a plasma sheath around antenna probes in a low‐density plasma. Approximate fits to the maximum refractive index and to the magnetic wave power profile of highly oblique waves are provided as a function of AE and L. Such fits shou. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025337 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025337
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Authors: Woodger L A, Millan R M, Li Z., and Sample J G
Title: Impact of Background Magnetic Field for EMIC Wave-Driven Electron Precipitation
Abstract: Wave‐particle interaction between relativistic electrons and electromagnetic ion cyclotron (EMIC) waves is a highly debated loss process contributing to the dynamics of Earth's radiation belts. Theoretical studies show that EMIC waves can result in strong loss of relativistic electrons in the radiation belts (Summers & Thorne, 2003, https://doi.org/10.1029/2002JA009489). However, many of these studies have not been validated by observations. Li et al. (2014, https://doi.org/10.1002/2014GL062273) modeled the relativistic electron precipitation observed by Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) in a single‐event case study based on a quasi‐linear diffusion model and observations by Van Allen Probes and GOES 13. We expand upon that study to investigate th. . .
Date: 10/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025315 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025315
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Authors: Takahashi Kazue, Denton Richard E, Motoba Tetsuo, Matsuoka Ayako, Kasaba Yasumasa, et al.
Title: Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed On and Off the Magnetic Equator
Abstract: The Arase spacecraft is capable of observing ultralow‐frequency waves in the inner magnetosphere at intermediate magnetic latitudes, a region sparsely covered by previous space craft missions. We report a series of impulsively excited fundamental toroidal mode standing Alfvén waves in the midnight sector observed by Arase outside the plasmasphere at magnetic latitudes 13–24° . The wave onsets are concurrent with Pi2 onsets detected by the Van Allen Probe B spacecraft at the magnetic equator in the duskside plasmasphere and by ground magnetometers at low latitudes. The duration of each toroidal wave packet is ∼20 min, which is much longer than that of the corresponding Pi2 wave packet. The toroidal waves cannot be the source of high‐latitude Pi2 waves because they were not detecte. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078731 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078731
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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: Remya B., Sibeck D G, Halford A J, Murphy K. R., Reeves G D, et al.
Title: Ion Injection Triggered EMIC Waves in the Earth's Magnetosphere
Abstract: We present Van Allen Probe observations of electromagnetic ion cyclotron (EMIC) waves triggered solely due to individual substorm‐injected ions in the absence of storms or compressions of the magnetosphere during 9 August 2015. The time at which the injected ions are observed directly corresponds to the onset of EMIC waves at the location of Van Allen Probe A (L = 5.5 and 18:06 magnetic local time). The injection was also seen at geosynchronous orbit by the Geostationary Operational Environmental Satellite and Los Alamos National Laboratory spacecraft, and the westward(eastward) drift of ions(electrons) was monitored by Los Alamos National Laboratory spacecraft at different local times. The azimuthal location of the injection was determined by tracing the injection signatures backward in. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025354 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025354
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Authors: Ukhorskiy A Y, Sorathia K. A., Merkin V. G., Sitnov M I, Mitchell D G, et al.
Title: Ion Trapping and Acceleration at Dipolarization Fronts: High-Resolution MHD/Test-Particle Simulations
Abstract: Much of plasma heating and transport from the magnetotail into the inner magnetosphere occurs in the form of mesoscale discrete injections associated with sharp dipolarizations of magnetic field (dipolarization fronts). In this paper we investigate the role of magnetic trapping in acceleration and transport of the plasmasheet ions into the ring current. For this purpose we use high‐resolution global MHD and three‐dimensional test‐particle simulations. It is shown that trapping, produced by sharp magnetic field gradients at the interface between dipolarizations and the ambient plasma, affect plasmasheet protons with energies above approximately 10 keV, enabling their transport across more than 10 Earth radii and acceleration by a factor of 10. Our estimates show that trapping is impor. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025370 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025370
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Authors: Su Zhenpeng, Liu Nigang, Zheng Huinan, Wang Yuming, and Wang Shui
Title: Large-Amplitude Extremely Low Frequency Hiss Waves in Plasmaspheric Plumes
Abstract: N/A
Date: 01/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL076754 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL076754/full
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Authors: áhlava J., ěmec F., ík O., šová I., Hospodarskyy G. B., et al.
Title: Longitudinal dependence of whistler mode electromagnetic waves in the Earth's inner magnetosphere
Abstract: We use the measurements performed by the DEMETER (2004‐2010) and the Van Allen Probes (2012‐2016, still operating) spacecraft to investigate the longitudinal dependence of the intensity of whistler mode waves in the Earth's inner magnetosphere. We show that a significant longitudinal dependence is observed inside the plasmasphere on the nightside, primarily in the frequency range 400 Hz–2 kHz. On the other hand, almost no longitudinal dependence is observed on the dayside. The obtained results are compared to the lightning occurrence rate provided by the OTD/LIS mission normalized by a factor accounting for the ionospheric attenuation. The agreement between the two dependencies indicates that lightning generated electromagnetic waves may be responsible for the observed effect, thus s. . .
Date: 07/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025284 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025284
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Authors: é M., Matsuoka A., Kumamoto A., Kasahara Y., Goldstein J, et al.
Title: Longitudinal Structure of Oxygen Torus in the Inner Magnetosphere: Simultaneous Observations by Arase and Van Allen Probe A
Abstract: Simultaneous observations of the magnetic field and plasma waves made by the Arase and Van Allen Probe A satellites at different magnetic local time (MLT) enable us to deduce the longitudinal structure of an oxygen torus for the first time. During 04:00–07:10 UT on 24 April 2017, Arase flew from L = 6.2 to 2.0 in the morning sector and detected an enhancement of the average plasma mass up to ~3.5 amu around L = 4.9–5.2 and MLT = 5.0 hr, implying that the plasma consists of approximately 15% O+ ions. Probe A moved outbound from L = 2.0 to 6.2 in the afternoon sector during 04:10–07:30 UT and observed no clear enhancements in the average plasma mass. For this event, the O+ density enhancement in the inner magnetosphere (i.e., oxygen torus) does not extend over all MLT but is skewed tow. . .
Date: 10/2018 Publisher: Geophysical Research Letters Pages: 10,177 - 10,184 DOI: 10.1029/2018GL080122 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080122
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Authors: Lejosne ène, and Mozer F S
Title: Magnetic activity dependence of the electric drift below L=3
Abstract: More than two years of magnetic and electric field measurements by the Van Allen Probes are analyzed with the objective of determining the average effects of magnetic activity on the electric drift below L=3. The study finds that an increase in magnetospheric convection leads to a decrease in the magnitude of the azimuthal component of the electric drift, especially in the night‐side. The amplitude of the slowdown is a function of L, local time MLT, and Kp, in a pattern consistent with the storm‐time dynamics of the ionosphere and thermosphere. To a lesser extent, magnetic activity also alters the average radial component of the electric drift below L=3. A global picture for the average variations of the electric drift with Kp is provided as a function of L and MLT. It is the first tim. . .
Date: 04/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL077873 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL077873
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Authors: Liu Nigang, Su Zhenpeng, Zheng Huinan, Wang Yuming, and Wang Shui
Title: Magnetosonic harmonic falling and rising frequency emissions potentially generated by nonlinear wave-wave interactions in the Van Allen radiation belts
Abstract: Magnetosonic waves play a potentially important role in the complex evolution of the radiation belt electrons. These waves typically appear as discrete emission lines along the proton gyrofrequency harmonics, consistent with the prediction of the local Bernstein mode instability of hot proton ring distributions. Magnetosonic waves are nearly dispersionless particularly at low harmonics and therefore have the roughly unchanged frequency‐time structures during the propagation. On the basis of Van Allen Probes observations, we here present the first report of magnetosonic harmonic falling and rising frequency emissions. They lasted for up to 2 h and occurred primarily in the dayside plasmatrough following intense substorms. These harmonic emission lines were well spaced by the proton gyrofr. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079232 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL079232
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Authors: Nishi Katsuki, Shiokawa Kazuo, and Spence Harlan
Title: Magnetospheric source region of auroral finger-like structures observed by the RBSP-A satellite
Abstract: Auroral finger‐like structures appear equatorward of the auroral oval in the diffuse auroral region and contribute to the auroral fragmentation into patches. A previous report of the first conjugate observation of auroral finger‐like structures using a THEMIS GBO camera and the THEMIS‐E satellite at a radial distance of ∼8 RE showed anti‐phase oscillations of magnetic and plasma pressures in the dawnside plasma sheet. In the present study, we report another simultaneous observation of auroral finger‐like structures at Gillam, Canada at ∼0900 UT (0230 magnetic local time) on November 14, 2014 with the RBSP satellites at 5.8 RE in the inner magnetosphere. From this simultaneous observation event, we obtained the following observations. (1) Auroral finger‐like structures devel. . .
Date: 08/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025480 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025480
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Authors: Engebretson M. J., Posch J. L., Capman N. S. S., Campuzano N. G., ělik P., et al.
Title: MMS, Van Allen Probes, GOES 13, and Ground Based Magnetometer Observations of EMIC Wave Events Before, During, and After a Modest Interplanetary Shock
Abstract: The stimulation of EMIC waves by a magnetospheric compression is perhaps the closest thing to a controlled experiment that is currently possible in magnetospheric physics, in that one prominent factor that can increase wave growth acts at a well‐defined time. We present a detailed analysis of EMIC waves observed in the outer dayside magnetosphere by the four Magnetosphere Multiscale (MMS) spacecraft, Van Allen Probe A, and GOES 13, and by four very high latitude ground magnetometer stations in the western hemisphere before, during, and after a modest interplanetary shock on December 14, 2015. Analysis shows several features consistent with current theory, as well as some unexpected features. During the most intense MMS wave burst, which began ~ 1 min after the end of a brief magnetosheat. . .
Date: 09/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025984 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025984
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Authors: Sorathia K. A., Ukhorskiy A Y, Merkin V. G., Fennell J. F., and Claudepierre S G
Title: Modeling the Depletion and Recovery of the Outer Radiation Belt During a Geomagnetic Storm: Combined MHD and Test Particle Simulations
Abstract: During geomagnetic storms the intensities of the outer radiation belt electron population can exhibit dramatic variability. Deep depletions in intensity during the main phase are followed by increases during the recovery phase, often to levels that significantly exceed their pre‐storm values. To study these processes, we simulate the evolution of the outer radiation belt during the 17 March 2013 geomagnetic storm using our newly‐developed radiation belt model (CHIMP) based on test particle and coupled 3D ring current and global MHD simulations, and driven solely with solar wind and F10.7 flux data. Our approach differs from previous work in that we use MHD information to identify regions of strong, bursty, and azimuthally localized Earthward convection in the magnetotail where test. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025506 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025506
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Authors: Selesnick R. S., Baker D N, Kanekal S G, Hoxie V C, and Li X
Title: Modeling the Proton Radiation Belt With Van Allen Probes Relativistic Electron-Proton Telescope Data
Abstract: An empirical model of the proton radiation belt is constructed from data taken during 2013–2017 by the Relativistic Electron-Proton Telescopes on the Van Allen Probes satellites. The model intensity is a function of time, kinetic energy in the range 18–600 MeV, equatorial pitch angle, and L shell of proton guiding centers. Data are selected, on the basis of energy deposits in each of the nine silicon detectors, to reduce background caused by hard proton energy spectra at low L. Instrument response functions are computed by Monte Carlo integration, using simulated proton paths through a simplified structural model, to account for energy loss in shielding material for protons outside the nominal field of view. Overlap of energy channels, their wide angular response, and changing satellit. . .
Date: 01/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024661 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024661/full
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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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Authors: Li Li, Zhou Xu-Zhi, Omura Yoshiharu, Wang Zi-Han, Zong Qiu-Gang, et al.
Title: Nonlinear drift resonance between charged particles and ultra-low frequency waves: Theory and Observations
Abstract: In Earth's inner magnetosphere, electromagnetic waves in the ultra‐low frequency (ULF) range play an important role in accelerating and diffusing charged particles via drift resonance. In conventional drift‐resonance theory, linearization is applied under the assumption of weak wave‐particle energy exchange so particle trajectories are unperturbed. For ULF waves with larger amplitudes and/or durations, however, the conventional theory becomes inaccurate since particle trajectories are strongly perturbed. Here, we extend the drift‐resonance theory into a nonlinear regime, to formulate nonlinear trapping of particles in a wave‐carried potential well, and predict the corresponding observable signatures such as rolled‐up structures in particle energy spectrum. After considering how. . .
Date: 08/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079038 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL079038
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Authors: Agapitov O., Drake J. F., Vasko I., Mozer F S, Artemyev A., et al.
Title: Nonlinear Electrostatic Steepening of Whistler Waves: The Guiding Factors and Dynamics in Inhomogeneous Systems
Abstract: Whistler mode chorus waves are particularly important in outer radiation belt dynamics due to their key role in controlling the acceleration and scattering of electrons over a very wide energy range. The efficiency of wave‐particle resonant interactions is defined by whistler wave properties which have been described by the approximation of plane linear waves propagating through the cold plasma of the inner magnetosphere. However, recent observations of extremely high‐amplitude whistlers suggest the importance of nonlinear wave‐particle interactions for the dynamics of the outer radiation belt. Oblique chorus waves observed in the inner magnetosphere often exhibit drastically nonsinusoidal (with significant power in the higher harmonics) waveforms of the parallel electric field, pres. . .
Date: 03/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL076957 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2017GL076957
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Authors: Takahashi Kazue, Lysak Robert, Vellante Massimo, Kletzing Craig A., Hartinger Michael D., et al.
Title: Observation and Numerical Simulation of Cavity Mode Oscillations Excited by an Interplanetary Shock
Abstract: Cavity mode oscillations (CMOs) are basic magnetohydrodynamic eigenmodes in the magnetosphere predicted by theory and are expected to occur following the arrival of an interplanetary shock. However, observational studies of shock-induced CMOs have been sparse. We present a case study of a dayside ultra-low-frequency (ULF) wave event that exhibited CMO properties. The event occurred immediately following the arrival of an interplanetary shock at 0829 UT on 15 August 2015. The shock was observed in the solar wind by the Time History of Events and Macroscale Interactions during Substorms-B and -C spacecraft, and magnetospheric ULF waves were observed by multiple spacecraft including the Van Allen Probes-A and -B spacecraft, which were located in the dayside plasmasphere at L∼ 1.4 and L∼ 2. . .
Date: 02/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024639 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024639/full
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Authors: Teng S., Zhao J., Tao X., Wang S., and Reeves G D
Title: Observation of Oblique Lower Band Chorus Generated by Nonlinear Three-Wave Interaction
Abstract: Oblique whistler mode waves have been suggested to play an important role in radiation belt electron dynamics. Recently, Fu et al. [2017] proposed that highly oblique lower band whistler waves could be generated by nonlinear three‐wave resonance. Here we present the first observational evidence of such process, using Van Allen Probes data, where an oblique lower band chorus wave is generated by two quasi‐parallel waves through nonlinear three‐wave interaction. The wave resonance condition is satisfied even in the presence of frequency chirping of one of the pump waves. Different from the simulation results of Fu et al. [2017], simultaneous particle data do not show a plateau in the electron distribution, which could be due to the very weak intensity of the generated waves. These resu. . .
Date: 06/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078765 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078765
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Authors: Ripoll ‐F., Loridan V., Denton M. H., Cunningham G., Reeves G., et al.
Title: Observations and Fokker‐Planck simulations of the L‐shell, energy, and pitch‐angle structure of Earth’s electron radiation belts during quiet times
Abstract: The evolution of the radiation belts in L‐shell (L), energy (E), and equatorial pitch‐angle (α0) is analyzed during the calm 11‐day interval (March 4 –March 15) following the March 1 storm 2013. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker‐Planck simulations combined with consistent event‐driven scattering modeling from whistler mode hiss waves. Three (L, E, α0)‐regions persist through 11 days of hiss wave scattering; the pitch‐angle dependent inner belt core (L~<2.2 and E<700 keV), pitch‐angle homogeneous outer belt low‐energy core (L>~5 and E~<100 keV), and a distinct pocket of electrons (L~[4.5, 5.5] and E~[0.7, 2] MeV). The pitch‐angle homogeneous outer belt is explained by the diff. . .
Date: 12/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026111 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026111
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Authors: Zhang Dianjun, Liu Wenlong, Li Xinlin, Sarris Theodore, Xiao Chao, et al.
Title: Observations of impulsive electric fields induced by Interplanetary Shock
Abstract: We investigate the characteristics of impulsive electric fields in Earth's magnetosphere, as measured by the Van Allen Probes, in association with interplanetary shocks, as measured by ACE and Wind spacecraft in the solar wind from January 2013 to July 2016. It is shown that electric field impulses are mainly induced by global compressions by the shocks, mostly in the azimuthal direction and the amplitudes of the initial electric field impulses are positively correlated with the rate of increase of dynamic pressure across the shock in the dayside. It is also shown that the temporal profile of the impulse is related to the temporal profile of the solar wind dynamic pressure, Pd. It is suggested that during the first period of the impulse the evolution of the electric field is directly contr. . .
Date: 07/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL078809 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL078809
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Authors: Zhang Zhenxia, Chen Lunjin, Li Xinqiao, Xia Zhiyang, Heelis Roderick A., et al.
Title: Observed propagation route of VLF transmitter signals in the magnetosphere
Abstract: Signals of powerful ground transmitters at various places have been detected by satellites in near‐Earth space. The study on propagation mode, ducted or nonducted, has attracted much attentions for several decades. Based on the statistical results from Van Allen Probes (data from Oct. 2012 to Mar. 2017) and DEMETER satellite (from Jan. 2006 to Dec. 2007), we present the ground transmitter signals distributed clearly in ionosphere and magnetosphere. The observed propagation route in the meridian plane in the magnetosphere for each of various transmitters from the combination of DEMETER and Van Allen Probes data in night time is revealed for the first time. We use realistic ray tracing simulation and compare simulation results against Van Allen Probes and DEMETER observation. By comparison. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025637 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025637
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Authors: Liu Xu, Chen Lunjin, Yang Lixia, Xia Zhiyang, and Malaspina David M.
Title: One-Dimensional Full Wave Simulation of Equatorial Magnetosonic Wave Propagation in an Inhomogeneous Magnetosphere
Abstract: The effect of the plasmapause on equatorially radially propagating fast magnetosonic (MS) waves in the Earth's dipole magnetic field is studied by using finite difference time domain method. We run 1-D simulation for three different density profiles: (1) no plasmapause, (2) with a plasmapause, and (3) with a plasmapause accompanied with fine-scale density irregularity. We find that (1) without plasmapause the radially inward propagating MS wave can reach ionosphere and continuously propagate to lower altitude if no damping mechanism is considered. The wave properties follow the cold plasma dispersion relation locally along its trajectory. (2) For simulation with a plasmapause with a scale length of 0.006 RE compared to wavelength, only a small fraction of the MS wave power is reflected by . . .
Date: 01/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024336 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024336/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: Bingham S. T., Mouikis C. G., Kistler L. M., Boyd A. J., Paulson K., et al.
Title: The outer radiation belt response to the storm time development of seed electrons and chorus wave activity during CME and CIR storms
Abstract: Gyroresonant wave‐particle interactions with very low frequency whistler mode chorus waves can accelerate subrelativistic seed electrons (hundreds of keV) to relativistic energies in the outer radiation belt during geomagnetic storms. In this study, we conduct a superposed epoch analysis of the chorus wave activity, the seed electron development, and the outer radiation belt electron response between L* = 2.5 and 5.5, for 25 coronal mass ejection and 35 corotating interaction region storms using Van Allen Probes observations. Electron data from the Magnetic Electron Ion Spectrometer and Relativistic Electron Proton Telescope instruments are used to monitor the storm‐phase development of the seed and relativistic electrons, and magnetic field measurements from the Electric and Magnetic . . .
Date: 12/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025963 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025963
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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: Eshetu W. W., Lyon J G, Hudson M K, and Wiltberger M. J.
Title: Pitch Angle Scattering of Energetic Electrons by BBFs
Abstract: Field line curvature scattering by the magnetic field structure associated with bursty bulk flows (BBFs) has been studied, using simulated output fields from the Lyon‐Fedder‐Mobarry global magnetohydrodynamic code for specified solar wind input. There are weak magnetic field strength (B) regions adjacent to BBFs observed in the simulations. We show that these regions can cause strong scattering where the first adiabatic invariant changes by several factors within one equatorial crossing of energetic electrons of a few kiloelectron volts when the BBFs are beyond 10RE geocentric in the tail. Scattering by BBFs decreases as they move toward the Earth or when the electron energy decreases. For radiation belt electrons near or inside geosynchronous orbit we demonstrate that the fields assoc. . .
Date: 10/2018 Publisher: Journal of Geophysical Research: Space Physics Pages: 9265 - 9274 DOI: 10.1029/2018JA025788 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025788
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Authors: Artemyev A. V., Zhang X.-J., Angelopoulos V, Runov A., Spence H E, et al.
Title: Plasma anisotropies and currents in the near-Earth plasma sheet and inner magnetosphere
Abstract: The region occupying radial distances of ∼3 − 9 Earth radii (RE) in the night side, includes the near‐Earth plasma sheet with stretched magnetic field lines and the inner magnetosphere with strong dipolar magnetic field. In this region, the plasma flow energy, which was injected into the inner magnetosphere from the magnetotail, is converted to particle heating and electromagnetic wave generation. These important processes are controlled by plasma anisotropies, which are the focus of this study. Using measurements of THEMIS and Van Allen Probes in this transition region we obtain radial profiles of ion and electron temperatures and anisotropies for various geomagnetic activity levels. Ion and electron anisotropies vary with the geomagnetic activity in opposite directions. Paralle. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025232 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025232
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Authors: Wang C., Rankin R, Wang Y., Zong Q.-G., Zhou X., et al.
Title: Poloidal mode wave-particle interactions inferred from Van Allen Probes and CARISMA ground-based observations
Abstract: Ultra‐low‐frequency (ULF) wave and test particle models are used to investigate the pitch angle and energy dependence of ion differential fluxes measured by the Van Allen Probes spacecraft on October 6th, 2012. Analysis of the satellite data reveals modulations in differential flux resulting from drift resonance between H+ ions and fundamental mode poloidal Alfvén waves detected near the magnetic equator at L∼5.7. Results obtained from simulations reproduce important features of the observations, including a substantial enhancement of the differential flux between ∼20° − 40° pitch angle for ion energies between ∼90 − 220keV, and an absence of flux modulations at 90°. The numerical results confirm predictions of drift‐bounce resonance theory and show good quantit. . .
Date: 05/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2017JA025123 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017JA025123
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Authors: Yuan Zhigang, Liu Kun, Yu Xiongdong, Yao Fei, Huang Shiyong, et al.
Title: Precipitation of radiation belt electrons by EMIC waves with conjugated observations of NOAA and Van Allen satellites
Abstract: In this letter, we present unique conjugated satellite observations of MeV relativistic electron precipitation caused by electromagnetic ion cyclotron (EMIC) waves. On the outer boundary of the plasmasphere, the Van Allen probe observed EMIC waves. At ionospheric altitudes, the NOAA 16 satellite at the footprint of Van Allen probe simultaneously detected obvious flux enhancements for precipitating >MeV radiation belt electrons, but not for precipitating MeV radiation belt electrons. Our result provides a direct magnetic conjugated observational link between in‐situ inner magnetospheric EMIC wav. . .
Date: 11/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080481 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080481
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Authors: Liu Nigang, Su Zhenpeng, Zheng Huinan, Wang Yuming, and Wang Shui
Title: Prompt Disappearance and Emergence of Radiation Belt Magnetosonic Waves Induced by Solar Wind Dynamic Pressure Variations
Abstract: Magnetosonic waves are highly oblique whistler mode emissions transferring energy from the ring current protons to the radiation belt electrons in the inner magnetosphere. Here we present the first report of prompt disappearance and emergence of magnetosonic waves induced by the solar wind dynamic pressure variations. The solar wind dynamic pressure reduction caused the magnetosphere expansion, adiabatically decelerated the ring current protons for the Bernstein mode instability, and produced the prompt disappearance of magnetosonic waves. On the contrary, because of the adiabatic acceleration of the ring current protons by the solar wind dynamic pressure enhancement, magnetosonic waves emerged suddenly. In the absence of impulsive injections of hot protons, magnetosonic waves were observa. . .
Date: 01/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL076382 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL076382/full
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Authors: Zhang X.-J., Thorne R., Artemyev A., Mourenas D., Angelopoulos V, et al.
Title: Properties of intense field-aligned lower-band chorus waves: Implications for nonlinear wave-particle interactions
Abstract: Resonant interactions between electrons and chorus waves are responsible for a wide range of phenomena in near‐Earth space (e.g., diffuse aurora, acceleration of MeV electrons, etc.). Although quasi‐linear diffusion is believed to be the primary paradigm for describing such interactions, an increasing number of investigations suggest that nonlinear effects are also important in controlling the rapid dynamics of electrons. However, present models of nonlinear wave‐particle interactions, which have been successfully used to describe individual short‐term events, are not directly applicable for a statistical evaluation of nonlinear effects and the long‐term dynamics of the outer radiation belt, because they lack information on the properties of intense (nonlinearly resonating with e. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025390 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025390
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Authors: Liu Si, Yan Qi, Yang Chang, Zhou Qinghua, He Zhaoguo, et al.
Title: Quantifying Extremely Rapid Flux Enhancements of Radiation Belt Relativistic Electrons Associated With Radial Diffusion
Abstract: Previous studies have revealed a typical picture that seed electrons are transported inward under the drive of radial diffusion and then accelerated via chorus to relativistic energies. Here we show a potentially different process during the 2–3 October 2013 storm when Van Allen Probes observed extremely rapid (by about 50 times in 2 h) flux enhancements of relativistic (1.8–3.4 MeV) electrons but without distinct chorus at lower L-shells. Meanwhile, Time History of Events and Macroscale Interactions during Substorms satellites simultaneously measured enhanced chorus and fluxes of energetic (∼100–300 keV) seed electrons at higher L-shells. Numerical calculations show that chorus can efficiently accelerate seed electrons at L ∼ 8.3. Then radial diffusion further increased the phas. . .
Date: 02/2018 Publisher: Geophysical Research Letters Pages: 1262 - 1270 DOI: 10.1002/grl.v45.310.1002/2017GL076513 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL076513/full
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Authors: Ma Q, Li W, Bortnik J, Thorne R M, Chu X., et al.
Title: Quantitative Evaluation of Radial Diffusion and Local Acceleration Processes During GEM Challenge Events
Abstract: We simulate the radiation belt electron flux enhancements during selected Geospace Environment Modeling (GEM) challenge events to quantitatively compare the major processes involved in relativistic electron acceleration under different conditions. Van Allen Probes observed significant electron flux enhancement during both the storm time of 17–18 March 2013 and non–storm time of 19–20 September 2013, but the distributions of plasma waves and energetic electrons for the two events were dramatically different. During 17–18 March 2013, the SYM‐H minimum reached −130 nT, intense chorus waves (peak Bw ~140 pT) occurred at 3.5 < L < 5.5, and several hundred keV to several MeV electron fluxes increased by ~2 orders of magnitude mostly at 3.5 < L < 5.5. During 19–20 September 2013, th. . .
Date: 03/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA025114 Available at: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017JA025114
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