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2019
Authors: Yuan Zhigang, Yao Fei, Yu Xiongdong, Huang Shiyong, and Ouyang Zhihai
Title: An Automatic Detection Algorithm Applied to Fast Magnetosonic Waves With Observations of the Van Allen Probes
Abstract: Fast magnetosonic (MS) waves can play an important role in the evolution of the inner magnetosphere. However, there is still not an effective method to quantitatively identify such waves for observations of the Van Allen Probes reasonably. In this paper, we used Van Allen Probes data from 18 September 2012 to 30 September 2014 to find a more comprehensive automatic detection algorithm for fast MS waves through statistical analysis of the major properties, including the planarity, ellipticity, and wave normal angle of whole fluctuations using the singular value decomposition method. According to a control variate method, we find an obvious difference between fast MS waves and other waves in the statistical distribution of their major properties. After eliminating the influence of background. . .
Date: Apr-05-2021 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026387 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026387
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Authors: Baker D.N., Zhao H., Li X, Kanekal S.G., Jaynes A.N., et al.
Title: Comparison of Van Allen Probes Energetic Electron Data with Corresponding GOES‐15 Measurements: 2012‐2018
Abstract: Electron fluxes (especially at energies E > 0.8 and >2 MeV) have been measured for many years by sensors on board the Geostationary Operational Environmental Satellite (GOES). These long‐term data (nominally at L~6.6) have become a mainstay for monitoring the Earth's radiation environment. We have carried out a study directly comparing the comprehensive radiation belt particle measurements from the NASA dual‐spacecraft Van Allen Probes (Radiation Belt Storm Probes) sensor systems with selected GOES operational data. The Van Allen Probes have measured the properties of radiation belt electrons virtually continuously from September 2012 through 2018. We make statistical comparisons of Van Allen Probes electron data near L=6 with concurrent daily averages of equivalent GOES‐15 flux . . .
Date: 11/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA027331 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA027331
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Authors: Baker D.N., Zhao H., Li X, Kanekal S.G., Jaynes A.N., et al.
Title: Comparison of Van Allen Probes Energetic Electron Data with Corresponding GOES‐15 Measurements: 2012‐2018
Abstract: Electron fluxes (especially at energies E > 0.8 and >2 MeV) have been measured for many years by sensors on board the Geostationary Operational Environmental Satellite (GOES). These long‐term data (nominally at L~6.6) have become a mainstay for monitoring the Earth's radiation environment. We have carried out a study directly comparing the comprehensive radiation belt particle measurements from the NASA dual‐spacecraft Van Allen Probes (Radiation Belt Storm Probes) sensor systems with selected GOES operational data. The Van Allen Probes have measured the properties of radiation belt electrons virtually continuously from September 2012 through 2018. We make statistical comparisons of Van Allen Probes electron data near L=6 with concurrent daily averages of equivalent GOES‐15 flux . . .
Date: 11/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA027331 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA027331
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Authors: Pinto V. A., Mourenas D., Bortnik J, Zhang X.‐J., Artemyev A. V., et al.
Title: Decay of Ultrarelativistic Remnant Belt Electrons Through Scattering by Plasmaspheric Hiss
Abstract: Ultrarelativistic electron remnant belts appear frequently following geomagnetic disturbances and are located in‐between the inner radiation belt and a reforming outer belt. As remnant belts are relatively stable, here we explore the importance of hiss and electromagnetic ion cyclotron waves in controlling the observed decay rates of remnant belt ultrarelativistic electrons in a statistical way. Using measurements from the Van Allen Probes inside the plasmasphere for 25 remnant belt events that occurred between 2012 and 2017 and that are located in the region 2.9Date: Dec-07-2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA026509 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA026509
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Authors: Yu J., Li L. Y., Cui J., Cao J. B., and Wang J.
Title: Effect of Low‐Harmonic Magnetosonic Waves on the Radiation Belt Electrons Inside the Plasmasphere
Abstract: In this paper, we presented two observational cases and simulations to indicate the relationship between the formation of butterfly‐like electron pitch angle distributions and the emission of low‐harmonic (LH) fast magnetosonic (MS) waves inside the high‐density plasmasphere. In the wave emission region, the pitch angle of relativistic (>1 MeV) electrons becomes obvious butterfly‐like distributions for both events (near‐equatorially mirroring electrons are transported to lower pitch angles). Unlike relativistic (>1 MeV) electrons, energetic electrons (<1 MeV) change slightly, except that relatively low‐energy electrons (<~150 keV) show butterfly‐like distributions in the 21 August 2013 event. In theory, the LH MS waves can affect different‐energy electrons through the bounc. . .
Date: 05/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026328 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026328
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Authors: Miyoshi Y, Matsuda S., Kurita S., Nomura K., Keika K, et al.
Title: EMIC waves converted from equatorial noise due to M/Q=2 ions in the plasmasphere: Observations from Van Allen Probes and Arase
Abstract: Equatorial noise (EN) emissions are observed inside and outside the plasmapause. EN emissions are referred to as magnetosonic mode waves. Using data from Van Allen Probes and Arase, we found conversion from EN emissions to electromagnetic ion cyclotron (EMIC) waves in the plasmasphere and in the topside ionosphere. A low frequency part of EN emissions becomes EMIC waves through branch splitting of EN emissions, and the mode conversion from EN to EMIC waves occurs around the frequency of M/Q=2 (deuteron and/or alpha particles) cyclotron frequency. These processes result in plasmaspheric EMIC waves. We investigated the ion composition ratio by characteristic frequencies of EN emissions and EMIC waves and obtained ion composition ratios. We found that the maximum composition ratio of M/Q=2 io. . .
Date: 04/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL083024 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL083024
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Authors: Miyoshi Y, Matsuda S., Kurita S., Nomura K., Keika K, et al.
Title: EMIC waves converted from equatorial noise due to M/Q=2 ions in the plasmasphere: Observations from Van Allen Probes and Arase
Abstract: Equatorial noise (EN) emissions are observed inside and outside the plasmapause. EN emissions are referred to as magnetosonic mode waves. Using data from Van Allen Probes and Arase, we found conversion from EN emissions to electromagnetic ion cyclotron (EMIC) waves in the plasmasphere and in the topside ionosphere. A low frequency part of EN emissions becomes EMIC waves through branch splitting of EN emissions, and the mode conversion from EN to EMIC waves occurs around the frequency of M/Q=2 (deuteron and/or alpha particles) cyclotron frequency. These processes result in plasmaspheric EMIC waves. We investigated the ion composition ratio by characteristic frequencies of EN emissions and EMIC waves and obtained ion composition ratios. We found that the maximum composition ratio of M/Q=2 io. . .
Date: 04/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL083024 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL083024
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Authors: Andreeva V. A., and Tsyganenko N A
Title: Empirical Modeling of the Geomagnetosphere for SIR and CME‐Driven Magnetic Storms
Abstract: During geomagnetic disturbances, the solar wind arrives in the form of characteristic sequences lasting from tens of hours to days. The most important magnetic storm drivers are the coronal mass ejections (CMEs) and the slow‐fast stream interaction regions (SIRs). Previous data‐based magnetic field models did not distinguish between these types of the solar wind driving. In the present work we retained the basic structure of the Tsyganenko and Andreeva (2015) model but fitted it to data samples corresponding to (1) SIR‐driven storms, (2) CME‐driven storms preceded with a shock ahead of the CME, and (3) CME‐driven storms without such shocks. The storm time dynamics of the model current systems has been represented using the parametrization method developed by Tsyganenko and Sitnov. . .
Date: 07/2019 Publisher: Journal of Geophysical Research: Space Physics Pages: 5641 - 5662 DOI: 10.1029/2018JA026008 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026008
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Authors: Andreeva V. A., and Tsyganenko N A
Title: Empirical Modeling of the Geomagnetosphere for SIR and CME‐Driven Magnetic Storms
Abstract: During geomagnetic disturbances, the solar wind arrives in the form of characteristic sequences lasting from tens of hours to days. The most important magnetic storm drivers are the coronal mass ejections (CMEs) and the slow‐fast stream interaction regions (SIRs). Previous data‐based magnetic field models did not distinguish between these types of the solar wind driving. In the present work we retained the basic structure of the Tsyganenko and Andreeva (2015) model but fitted it to data samples corresponding to (1) SIR‐driven storms, (2) CME‐driven storms preceded with a shock ahead of the CME, and (3) CME‐driven storms without such shocks. The storm time dynamics of the model current systems has been represented using the parametrization method developed by Tsyganenko and Sitnov. . .
Date: 07/2019 Publisher: Journal of Geophysical Research: Space Physics Pages: 5641 - 5662 DOI: 10.1029/2018JA026008 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026008
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Authors: Andreeva V. A., and Tsyganenko N A
Title: Empirical Modeling of the Geomagnetosphere for SIR and CME‐Driven Magnetic Storms
Abstract: During geomagnetic disturbances, the solar wind arrives in the form of characteristic sequences lasting from tens of hours to days. The most important magnetic storm drivers are the coronal mass ejections (CMEs) and the slow‐fast stream interaction regions (SIRs). Previous data‐based magnetic field models did not distinguish between these types of the solar wind driving. In the present work we retained the basic structure of the Tsyganenko and Andreeva (2015) model but fitted it to data samples corresponding to (1) SIR‐driven storms, (2) CME‐driven storms preceded with a shock ahead of the CME, and (3) CME‐driven storms without such shocks. The storm time dynamics of the model current systems has been represented using the parametrization method developed by Tsyganenko and Sitnov. . .
Date: 07/2019 Publisher: Journal of Geophysical Research: Space Physics Pages: 5641 - 5662 DOI: 10.1029/2018JA026008 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026008
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Authors: Stephens G. K., Sitnov M I, Korth H., Tsyganenko N A, Ohtani S, et al.
Title: Global Empirical Picture of Magnetospheric Substorms Inferred From Multimission Magnetometer Data
Abstract: Magnetospheric substorms represent key explosive processes in the interaction of the Earth's magnetosphere with the solar wind, and their understanding and modeling are critical for space weather forecasting. During substorms, the magnetic field on the nightside is first stretched in the antisunward direction and then it rapidly contracts earthward bringing hot plasmas from the distant space regions into the inner magnetosphere, where they contribute to geomagnetic storms and Joule dissipation in the polar ionosphere, causing impressive splashes of aurora. Here we show for the first time that mining millions of spaceborne magnetometer data records from multiple missions allows one to reconstruct the global 3‐D picture of these stretching and dipolarization processes. Stretching results i. . .
Date: 01/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025843 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025843
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Authors: Ma Q, Li W, Bortnik J, Kletzing C A, Kurth W S, et al.
Title: Global Survey and Empirical Model of Fast Magnetosonic Waves Over Their Full Frequency Range in Earth's Inner Magnetosphere
Abstract: We investigate the global distribution and provide empirical models of fast magnetosonic waves using the combined observations by the magnetometer and waveform receiver on board Van Allen Probes. The magnetometer measurements of magnetosonic waves indicate a significant wave power within the frequency range from the helium gyrofrequency to 20 Hz at L ≥ 4 in the afternoon sector, both inside and outside the plasmapause. The waveform receiver measurements indicate a significant wave power from 20 Hz to the lower hybrid resonance frequency at L ≤ 5.5 near the dayside outside the plasmapause or in the afternoon sector inside the plasmapause. The sum of the wave powers from the two instruments provides the wave power distribution over the complete frequency range. The most significant root. . .
Date: 12/2019 Publisher: Journal of Geophysical Research: Space Physics Pages: 10270 - 10282 DOI: 10.1029/2019JA027407 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA027407
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Authors: Qin Murong, Hudson Mary, Li Zhao, Millan Robyn, Shen Xiaochen, et al.
Title: Investigating Loss of Relativistic Electrons Associated With EMIC Waves at Low L Values on 22 June 2015
Abstract: In this study, rapid loss of relativistic radiation belt electrons at low L* values (2.4–3.2) during a strong geomagnetic storm on 22 June 2015 is investigated along with five possible loss mechanisms. Both the particle and wave data are obtained from the Van Allen Probes. Duskside H+ band electromagnetic ion cyclotron (EMIC) waves were observed during a rapid decrease of relativistic electrons with energy above 5.2 MeV occurring outside the plasmasphere during extreme magnetopause compression. Lower He+ composition and enriched O+ composition are found compared to typical values assumed in other studies of cyclotron resonant scattering of relativistic electrons by EMIC waves. Quantitative analysis demonstrates that even with the existence of He+ band EMIC waves, it is the H+ band EMIC w. . .
Date: 05/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025726 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025726
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Authors: Ozeke L. G., Mann I. R., Claudepierre S G, Henderson M., Morley S. K., et al.
Title: The March 2015 Superstorm Revisited: Phase Space Density Profiles and Fast ULF Wave Diffusive Transport
Abstract: We present the temporal evolution of electron Phase Space Density (PSD) in the outer radiation belt during the intense March 2015 geomagnetic storm. Comparing observed PSD profiles as a function of L* at fixed first, M, and second, K, adiabatic invariants with those produced by simulations is critical for determining the physical processes responsible for the outer radiation belt dynamics. Here we show that the bulk of the accelerated and enhanced outer radiation belt population consists of electrons with K < 0.17 G1/2Re. For these electrons, the observed PSD versus L* profiles during the recovery phase of the storm have a positive radial gradient. We compare the observed temporal evolution of the PSD profiles during the recovery phase with those produced by radial diffusion simulations dr. . .
Date: 01/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026326 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026326
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Authors: Zhu Hui, Chen Lunjin, Liu Xu, and Shprits Yuri Y
Title: Modulation of Locally Generated Equatorial Noise by ULF Wave
Abstract: In this paper we report a rare and fortunate event of fast magnetosonic (MS, also called equatorial noise) waves modulated by compressional ultralow frequency (ULF) waves measured by Van Allen Probes. The characteristics of MS waves, ULF waves, proton distribution, and their potential correlations are analyzed. The results show that ULF waves can modulate the energetic ring proton distribution and in turn modulate the MS generation. Furthermore, the variation of MS intensities is attributed to not only ULF wave activities but also the variation of background parameters, for example, number density. The results confirm the opinion that MS waves are generated by proton ring distribution and propose a new modulation phenomenon.
Date: 04/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026199 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026199
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Authors: Kilpua E. K. J., Turner D. L., Jaynes A. N., Hietala H., Koskinen H. E. J., et al.
Title: Outer Van Allen Radiation Belt Response to Interacting Interplanetary Coronal Mass Ejections
Abstract: We study the response of the outer Van Allen radiation belt during an intense magnetic storm on 15–22 February 2014. Four interplanetary coronal mass ejections (ICMEs) arrived at Earth, of which the three last ones were interacting. Using data from the Van Allen Probes, we report the first detailed investigation of electron fluxes from source (tens of kiloelectron volts) to core (megaelectron volts) energies and possible loss and acceleration mechanisms as a response to substructures (shock, sheath and ejecta, and regions of shock‐compressed ejecta) in multiple interacting ICMEs. After an initial enhancement induced by a shock compression of the magnetosphere, core fluxes strongly depleted and stayed low for 4 days. This sustained depletion can be related to a sequence of ICME substruc. . .
Date: 03/2019 Publisher: Journal of Geophysical Research: Space Physics Pages: 1927 - 1947 DOI: 10.1029/2018JA026238 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026238
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Authors: Kilpua E. K. J., Turner D. L., Jaynes A. N., Hietala H., Koskinen H. E. J., et al.
Title: Outer Van Allen Radiation Belt Response to Interacting Interplanetary Coronal Mass Ejections
Abstract: We study the response of the outer Van Allen radiation belt during an intense magnetic storm on 15–22 February 2014. Four interplanetary coronal mass ejections (ICMEs) arrived at Earth, of which the three last ones were interacting. Using data from the Van Allen Probes, we report the first detailed investigation of electron fluxes from source (tens of kiloelectron volts) to core (megaelectron volts) energies and possible loss and acceleration mechanisms as a response to substructures (shock, sheath and ejecta, and regions of shock‐compressed ejecta) in multiple interacting ICMEs. After an initial enhancement induced by a shock compression of the magnetosphere, core fluxes strongly depleted and stayed low for 4 days. This sustained depletion can be related to a sequence of ICME substruc. . .
Date: 03/2019 Publisher: Journal of Geophysical Research: Space Physics Pages: 1927 - 1947 DOI: 10.1029/2018JA026238 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026238
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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: 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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Authors: Nakamura S., Omura Y., Kletzing C., and Baker D N
Title: Rapid Precipitation of Relativistic Electron by EMIC Rising‐Tone Emissions Observed by the Van Allen Probes
Abstract: On 23 February 2014, Van Allen Probes sensors observed quite strong electromagnetic ion cyclotron (EMIC) waves in the outer dayside magnetosphere. The maximum amplitude was more than 14 nT, comparable to 7% of the magnitude of the ambient magnetic field. The EMIC waves consisted of a series of coherent rising tone emissions. Rising tones are excited sporadically by energetic protons. At the same time, the probes detected drastic fluctuations in fluxes of MeV electrons. It was found that the electron fluxes decreased by more than 30% during the 1 min following the observation of each EMIC rising tone emissions. Furthermore, it is concluded that the flux reduction is a nonadiabatic (irreversible) process since holes in the particle flux levels appear as drift echoes with energy dispersion. W. . .
Date: May-08-2020 Publisher: Journal of Geophysical Research: Space Physics Pages: 6701 - 6714 DOI: 10.1029/2019JA026772 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA026772
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Authors: Nakamura S., Omura Y., Kletzing C., and Baker D N
Title: Rapid Precipitation of Relativistic Electron by EMIC Rising‐Tone Emissions Observed by the Van Allen Probes
Abstract: On 23 February 2014, Van Allen Probes sensors observed quite strong electromagnetic ion cyclotron (EMIC) waves in the outer dayside magnetosphere. The maximum amplitude was more than 14 nT, comparable to 7% of the magnitude of the ambient magnetic field. The EMIC waves consisted of a series of coherent rising tone emissions. Rising tones are excited sporadically by energetic protons. At the same time, the probes detected drastic fluctuations in fluxes of MeV electrons. It was found that the electron fluxes decreased by more than 30% during the 1 min following the observation of each EMIC rising tone emissions. Furthermore, it is concluded that the flux reduction is a nonadiabatic (irreversible) process since holes in the particle flux levels appear as drift echoes with energy dispersion. W. . .
Date: May-08-2020 Publisher: Journal of Geophysical Research: Space Physics Pages: 6701 - 6714 DOI: 10.1029/2019JA026772 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA026772
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Authors: Boyd A. J., Reeves G D, Spence H E, Funsten H O, Larsen B A, et al.
Title: RBSP‐ECT Combined Spin‐Averaged Electron Flux Data Product
Abstract: We describe a new data product combining the spin‐averaged electron flux measurements from the Radiation Belt Storm Probes (RBSP) Energetic Particle Composition and Thermal Plasma (ECT) suite on the National Aeronautics and Space Administration's Van Allen Probes. We describe the methodology used to combine each of the data sets and produce a consistent set of spectra for September 2013 to the present. Three‐minute‐averaged flux spectra are provided spanning energies from 15 eV up to 20 MeV. This new data product provides additional utility to the ECT data and offers a consistent cross calibrated data set for researchers interested in examining the dynamics of the inner magnetosphere across a wide range of energies.
Date: 10/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA026733 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA026733
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Authors: Yuan Zhigang, Yu Xiongdong, Ouyang Zhihai, Yao Fei, Huang Shiyong, et al.
Title: Simultaneous trapping of EMIC and MS waves by background plasmas
Abstract: Electromagnetic ion cyclotron waves and fast magnetosonic waves are found to be simultaneously modulated by background plasma density: both kinds of waves were observed in high plasma density regions but vanished in low density regions. Theoretical analysis based on Snell's law and linear growth theory have been utilized to investigate the physical mechanisms driving such modulation. It is suggested that the modulation of fast magnetosonic waves might be due to trapping by plasma density structures, which results from a conservation of the parameter Q during their propagation. Here Q = nrsinψ, with n the refractive index, r the radial distance, and ψ the wave azimuthal angle. As for electromagnetic ion cyclotron waves, the modulation might be owed to the ion composition difference betwee. . .
Date: 02/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026149 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026149
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Authors: Shen Xiao‐Chen, Li Wen, Ma Qianli, Agapitov Oleksiy, and Nishimura Yukitoshi
Title: Statistical Analysis of Transverse Size of Lower Band Chorus Waves Using Simultaneous Multisatellite Observations
Abstract: Chorus waves are known to accelerate or scatter energetic electrons via quasi‐linear or nonlinear wave‐particle interactions in the Earth's magnetosphere. In this letter, by taking advantage of simultaneous observations of chorus waveforms from at least a pair of probes among Van Allen Probes and/or Time History of Events and Macroscale Interactions during Substorms (THEMIS) missions, we statistically calculate the transverse size of lower band chorus wave elements. The average size of lower band chorus wave element is found to be ~315±32 km over L shells of ~5–6. Furthermore, our results suggest that the scale size of lower band chorus tends to be (1) larger at higher L shells; (2) larger at higher magnetic latitudes, especially on the dayside; and (3) larger in the azimuthal direc. . .
Date: 05/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL083118 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL083118
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Authors: Tyler E., Breneman A., Cattell C., Wygant J, Thaller S., et al.
Title: Statistical Distribution of Whistler Mode Waves in the Radiation Belts With Large Magnetic Field Amplitudes and Comparison to Large Electric Field Amplitudes
Abstract: We present a statistical analysis with 100% duty cycle and non‐time‐averaged amplitudes of the prevalence and distribution of high‐amplitude >50‐pT whistler mode waves in the outer radiation belt using 5 years of Van Allen Probes data. Whistler mode waves with high magnetic field amplitudes are most common above L=4.5 and between magnetic local time of 0–14 where they are present approximately 1–6% of the time. During high geomagnetic activity, high‐amplitude whistler mode wave occurrence rises above 25% in some regions. The dayside population are more common during quiet or moderate geomagnetic activity and occur primarily >5° from the magnetic equator, while the night‐to‐dawn population are enhanced during active times and are primarily within 5° of the magnetic equat. . .
Date: 07/2019 Publisher: Journal of Geophysical Research: Space Physics Pages: 6541 - 6552 DOI: 10.1029/2019JA026913 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA026913
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Authors: Tyler E., Breneman A., Cattell C., Wygant J, Thaller S., et al.
Title: Statistical Distribution of Whistler Mode Waves in the Radiation Belts With Large Magnetic Field Amplitudes and Comparison to Large Electric Field Amplitudes
Abstract: We present a statistical analysis with 100% duty cycle and non‐time‐averaged amplitudes of the prevalence and distribution of high‐amplitude >50‐pT whistler mode waves in the outer radiation belt using 5 years of Van Allen Probes data. Whistler mode waves with high magnetic field amplitudes are most common above L=4.5 and between magnetic local time of 0–14 where they are present approximately 1–6% of the time. During high geomagnetic activity, high‐amplitude whistler mode wave occurrence rises above 25% in some regions. The dayside population are more common during quiet or moderate geomagnetic activity and occur primarily >5° from the magnetic equator, while the night‐to‐dawn population are enhanced during active times and are primarily within 5° of the magnetic equat. . .
Date: 07/2019 Publisher: Journal of Geophysical Research: Space Physics Pages: 6541 - 6552 DOI: 10.1029/2019JA026913 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA026913
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Authors: Mitani K., Seki K., Keika K, Gkioulidou M., Lanzerotti L J, et al.
Title: Statistical Study of Selective Oxygen Increase in High‐Energy Ring Current Ions During Magnetic Storms
Abstract: Ion transport from the plasma sheet to the ring current is the main cause of the development of the ring current. Energetic (>150 keV) ring current ions are known to be transported diffusively in several days. A recent study suggested that energetic oxygen ions are transported closer to the Earth than protons due to the diffusive transport caused by a combination of the drift and drift‐bounce resonances with Pc 3–5 ultralow frequency waves during the 24 April 2013 magnetic storm. To understand the occurrence conditions of such selective oxygen increase (SOI), we investigate the phase space densities (PSDs) between protons and oxygen ions with the first adiabatic invariants (μ) of 0.1–2.0 keV/nT measured by the Radiation Belt Storm Probes Ion Composition Experiment instrument on the . . .
Date: 04/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026168 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026168
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Authors: Drozdov A. Y., Aseev N., Effenberger F., Turner D. L., Saikin A., et al.
Title: Storm Time Depletions of Multi‐MeV Radiation Belt Electrons Observed at Different Pitch Angles
Abstract: During geomagnetic storms, the rapid depletion of the high‐energy (several MeV) outer radiation belt electrons is the result of loss to the interplanetary medium through the magnetopause, outward radial diffusion, and loss to the atmosphere due to wave‐particle interactions. We have performed a statistical study of 110 storms using pitch angle resolved electron flux measurements from the Van Allen Probes mission and found that inside of the radiation belt (L* = 3 − 5) the number of storms that result in depletion of electrons with equatorial pitch angle αeq = 30∘ is higher than number of storms that result in depletion of electrons with equatorial pitch angle αeq = 75∘. We conclude that this result is consistent with electron scattering by whistler and electromagnetic ion cyclo. . .
Date: 11/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA027332 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA027332
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Authors: Agapitov O., Mourenas D., Artemyev A., Hospodarsky G., and Bonnell J.W.
Title: Timescales for electron quasi‐linear diffusion by lower‐band chorus waves: the effects of ω pe / Ω ce dependence on geomagnetic activity
Abstract: Electron scattering by chorus waves is an important mechanism that can lead to fast electron acceleration and loss in the outer radiation belt. Making use of Van Allen Probes measurements, we present the first statistical survey of megaelectron volt electron pitch angle and energy quasi‐linear diffusion rates by chorus waves as a function of L‐shell, local time, and AE index, taking into account the local electron plasma frequency to gyrofrequency ratio ωpe/Ωce, chorus wave frequency, and resonance wave amplitude. We demonstrate that during disturbed periods, ωpe/Ωce strongly decreases in the night sector, leading to a faster electron loss but also a much faster electron energization in two distinct regions just above the plasmapause and at L ~ 3.5–5.5. Spatiotemporal variations . . .
Date: 05/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL083446 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL083446
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Authors: Watt C. E. J., Allison H. J., Meredith N P, Thompson R. L., Bentley S. N., et al.
Title: Variability of Quasilinear Diffusion Coefficients for Plasmaspheric Hiss
Abstract: In the outer radiation belt, the acceleration and loss of high‐energy electrons is largely controlled by wave‐particle interactions. Quasilinear diffusion coefficients are an efficient way to capture the small‐scale physics of wave‐particle interactions due to magnetospheric wave modes such as plasmaspheric hiss. The strength of quasilinear diffusion coefficients as a function of energy and pitch angle depends on both wave parameters and plasma parameters such as ambient magnetic field strength, plasma number density, and composition. For plasmaspheric hiss in the magnetosphere, observations indicate large variations in the wave intensity and wave normal angle, but less is known about the simultaneous variability of the magnetic field and number density. We use in situ measurements. . .
Date: 10/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA026401 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA026401
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Authors: Pandya Megha, Veenadhari B., Ebihara Y., Kanekal S.G., and Baker D.N.
Title: Variation of Radiation belt electron flux during CME and CIR driven geomagnetic storms: Van Allen Probes observations
Abstract: Relativistic electron flux responses in the inner magnetosphere are investigated for 28 magnetic storms driven by Corotating Interaction Region (CIR) and 27 magnetic storms driven by Coronal Mass Ejection (CME), using data from the Relativistic Electron‐Proton Telescope (REPT) instrument on board Van‐Allen Probes from Oct‐2012 to May‐2017. In this present study we analyze the role of CIRs and CMEs in electron dynamics by sorting the electron fluxes in terms of averaged solar wind parameters, L‐values, and energies. The major outcomes from our study are: (i) At L = 3 and E = 3.4 MeV, for >70% cases the electron flux remains stable, while at L = 5, for ~82% cases it changes with the geomagnetic conditions. (ii) At L = 5, ~53% of the CIR storms and 30% of the CME storms show electro. . .
Date: 07/2019 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2019JA026771 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JA026771
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2018
Authors: Pinto Víctor A., Bortnik Jacob, Moya Pablo S., Lyons Larry R., Sibeck David G., et al.
Title: Characteristics, Occurrence and Decay Rates of Remnant Belts associated with Three-Belt events in the Earth's Radiation Belts
Abstract: Shortly after the launch of the Van Allen Probes, a new three‐belt configuration of the electron radiation belts was reported. Using data between September 2012 and November 2017, we have identified 30 three‐belt events and found that about 18% of geomagnetic storms result in such configuration. Based on the identified events, we evaluated some characteristics of the remnant (intermediate) belt. We determined the energy range of occurrence and found it peaks at E = 5.2 MeV. We also determined that the magnetopause location and SYM‐H value may play an important role in the outer belt losses that lead to formation and location of the remnant belt. Finally, we calculated the decay rates of the remnant belt for all events and found that their lifetime gets longer as energy increases,. . .
Date: 10/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080274 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080274
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Authors: Yuan Zhigang, Yu Xiongdong, Huang Shiyong, Qiao Zheng, Yao Fei, et al.
Title: Cold Ion Heating by Magnetosonic Waves in a Density Cavity of the Plasmasphere
Abstract: Fast magnetosonic (MS) waves play an important role in the dynamics of the inner magnetosphere. Theoretical prediction and simulation have demonstrated that MS waves can heat cold ions. However, direct observational evidence of cold ion heating by MS waves has so far remained elusive. In this paper, we show a typical event of cold ion heating by magnetosonic waves in a density cavity of the plasmasphere with observations of the Van Allen Probe mission on 22 August 2013. During enhancements of the MS wave intensity in the density cavity, the fluxes of trapped H+ and He+ ions with energies of 10–100 eV were observed to increase, implying that cold plasmaspheric ions were heated through high-order resonances with the MS waves. Based on simultaneous observations of ring current protons, we h. . .
Date: 02/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024919 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024919/full
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Authors: Hua Man, Ni Binbin, Fu Song, Gu Xudong, Xiang Zheng, et al.
Title: Combined Scattering of Outer Radiation Belt Electrons by Simultaneously Occurring Chorus, Exohiss, and Magnetosonic Waves
Abstract: We report a typical event that fast magnetosonic (MS) waves, exohiss, and two‐band chorus waves occurred simultaneously on the dayside observed by Van Allen Probes on 25 December 2013. By combining calculations of electron diffusion coefficients and 2‐D Fokker‐Planck diffusion simulations, we quantitatively analyze the combined scattering effect of multiple waves to demonstrate that the net impact of combined scattering does not simply depend on the wave intensity dominance of various plasma waves. Although the observed MS waves are most intense, the electron butterfly distribution is inhibited by exohiss and chorus, and electrons are considerably accelerated by combined scattering of MS and chorus waves. The simulated electron pitch angle distributions exhibit the variation trend co. . .
Date: 09/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079533 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL079533
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Authors: Ren Jie, Zong Qiu-Gang, Miyoshi Yoshizumi, Rankin Robert, Spence Harlan E, et al.
Title: A comparative study of ULF waves' role in the dynamics of charged particles in the plasmasphere: Van Allen Probes observation
Abstract: By analyzing observations from Van Allen Probes in its inbound and outbound orbits, we present evidence of coherent enhancement of cold plasmaspheric electrons and ions due to drift‐bounce resonance with ULF waves. From 18:00 UT on 28 May 2017 to 10:00 UT on 29 May 2017, newly formed poloidal mode standing ULF waves with significant electric field oscillations were observed in two consecutive orbits when Probe B was travelling inbound. In contrast to observations during outbound orbits, the cold (< 150 eV) electorns measured by the HOPE instrument were characterized by flux enhancements several times larger and bi‐directional pitch angle distributions during inbound orbits. The electron number density inferred from upper hybrid waves is twice as larger as during inbound orbits, which w. . .
Date: 06/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025255 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025255
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Authors: Murphy Kyle R., Inglis Andrew R., Sibeck David G., Rae Jonathan, Watt Clare E. J., et al.
Title: Determining the mode, frequency, and azimuthal wave number of ULF waves during a HSS and moderate geomagnetic storm
Abstract: Ultra‐low frequency (ULF) waves play a fundamental role in the dynamics of the inner‐magnetosphere and outer radiation belt during geomagnetic storms. Broadband ULF wave power can transport energetic electrons via radial diffusion and discrete ULF wave power can energize electrons through a resonant interaction. Using observations from the Magnetospheric Multiscale (MMS) mission, we characterize the evolution of ULF waves during a high‐speed solar wind stream (HSS) and moderate geomagnetic storm while there is an enhancement of the outer radiation belt. The Automated Flare Inference of Oscillations (AFINO) code is used to distinguish discrete ULF wave power from broadband wave power during the HSS. During periods of discrete wave power and utilizing the close separation of the MMS sp. . .
Date: 05/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2017JA024877 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017JA024877
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Authors: Liu Bin, Li Liuyuan, Yu Jiang, and Cao Jinbin
Title: The Effect of Hot Protons on Magnetosonic Waves Inside and Outside the Plasmapause: New Observations and Theoretic Results
Abstract: Based on the wave and proton observations by Van Allen Probes A and B, we examined the effects of hot protons (0.01–50 keV) on fast magnetosonic (MS) waves inside and outside the Earth's plasmasphere. In the low-density plasma trough outside the plasmapause, the gyroresonance interactions between hot protons and MS waves not only cause the MS wave growth at some frequencies but also lead to the damping of MS waves at other frequencies, which depends on the proton phase space density gradient and the ambient plasma density. The gyroresonance of the observed hot protons cannot excite MS waves near the lower hybrid resonance frequency and even causes the MS wave damping. Thus, the frequencies of the observed MS waves outside the plasmapause are usually lower than the lower hybrid resonance . . .
Date: 01/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024676 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024676/full
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Authors: Liu Bin, Li Liuyuan, Yu Jiang, and Cao Jinbin
Title: The Effect of Hot Protons on Magnetosonic Waves Inside and Outside the Plasmapause: New Observations and Theoretic Results
Abstract: Based on the wave and proton observations by Van Allen Probes A and B, we examined the effects of hot protons (0.01–50 keV) on fast magnetosonic (MS) waves inside and outside the Earth's plasmasphere. In the low-density plasma trough outside the plasmapause, the gyroresonance interactions between hot protons and MS waves not only cause the MS wave growth at some frequencies but also lead to the damping of MS waves at other frequencies, which depends on the proton phase space density gradient and the ambient plasma density. The gyroresonance of the observed hot protons cannot excite MS waves near the lower hybrid resonance frequency and even causes the MS wave damping. Thus, the frequencies of the observed MS waves outside the plasmapause are usually lower than the lower hybrid resonance . . .
Date: 01/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024676 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024676/full
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Authors: Mager Pavel N., Mikhailova Olga S., Mager Olga V., and Klimushkin Dmitri Yu.
Title: Eigenmodes of the transverse Alfvénic resonator at the plasmapause: a Van Allen Probes case study
Abstract: A Pc4 ULF wave was detected at spacecraft B of the Van Allen Probes at the plasmapause. A distinctive feature of this wave is the strong periodical modulation of the wave. It is assumed that this modulation is a beating of oscillations close in frequency: at least two harmonics with frequencies of 15.3 and 13.6 MHz are found. It is shown that these harmonics can be the eigenmodes of the transverse resonator at the local maximum of the Alfvén velocity. In addition, the observed wave was in a drift resonance with energetic 80 keV protons and could be generated by an unstable “bump on tail” distribution of protons simultaneously observed with the wave. The estimate of the azimuthal wave number m made from the drift resonance condition gives a value of about −100, i.e., it is a westward. . .
Date: 09/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL079596 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL079596
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Authors: Bin Kang Suk-, Fok Mei-Ching, Komar Colin, Glocer Alex, Li Wen, et al.
Title: An energetic electron flux dropout due to magnetopause shadowing on 1 June 2013
Abstract: We examine the mechanisms responsible for the dropout of energetic electron flux during 31 May – 1 June 2013, using Van Allen Probe (RBSP) electron flux data and simulations with the Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. During storm main phase, L-shells at RBSP locations are greater than ~ 8, which are connected to open drift shells. Consequently, diminished electron fluxes were observed over a wide range of energies. The combination of drift shell splitting, magnetopause shadowing and drift loss all result in butterfly electron pitch-angle distributions (PADs) at the nightside. During storm sudden commencement, RBSP observations display electron butterfly PADs over a wide range of energies. However, it is difficult to determine whether there are butterfly PADs duri. . .
Date: 01/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2017JA024879 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017JA024879/full
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Authors: Sandhu J. K., Rae I. J., Freeman M. P., Forsyth C., Gkioulidou M., et al.
Title: Energisation of the ring current by substorms
Abstract: The substorm process releases large amounts of energy into the magnetospheric system, although where the energy is transferred to and how it is partitioned remains an open question. In this study, we address whether the substorm process contributes a significant amount of energy to the ring current. The ring current is a highly variable region, and understanding the energisation processes provides valuable insight into how substorm ‐ ring current coupling may contribute to the generation of storm conditions and provide a source of energy for wave driving. In order to quantify the energy input into the ring current during the substorm process, we analyse RBSPICE and HOPE ion flux measurements for H+, O+, and He+. The energy content of the ring current is estimated and binned spatially for. . .
Date: 09/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025766 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025766
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Authors: 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: 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: 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: 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: 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: 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: 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: Mitani K., Seki K., Keika K, Gkioulidou M., Lanzerotti L J, et al.
Title: Radial Transport of Higher-Energy Oxygen Ions Into the Deep Inner Magnetosphere Observed by Van Allen Probes
Abstract: The transport mechanism of the ring current ions differs among ion energies. Lower‐energy (≲150 keV) ions are well known to be transported convectively. Higher‐energy (≳150 keV) protons are reported to be transported diffusively, while there are few reports about transport of higher‐energy oxygen ions. We report the radial transport of higher‐energy oxygen ions into the deep inner magnetosphere during the late main phase of the magnetic storm on 23–25 April 2013 observed by the Van Allen Probes spacecraft. An enhancement of 1–100 mHz magnetic fluctuations is simultaneously observed. Observations of 3 and 30 mHz geomagnetic pulsations indicate the azimuthal mode number is ≤10. The fluctuations can resonate with the drift and bounce motions of the oxygen ions. The results s. . .
Date: 05/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL077500 Available at: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL077500
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Authors: Xiong Ying, Xie Lun, Chen Lunjin, Ni Binbin, Fu Suiyan, et al.
Title: The Response of the Energy Content of the Outer Electron Radiation Belt to Geomagnetic Storms
Abstract: Using the data from the Van Allen Probe‐A spacecraft, the variability of the total outer radiation belt (2.5300 keV) is investigated for the first time during 51 isolated storms spanning from October 2012 to May 2017. The statistical results show that the TRBEEC exhibits no‐change in 20% of the storms and gets enhanced during 80% of them. The sub‐relativistic electrons (300‐500 keV) and relativistic electrons (0.5‐2.0 MeV) equally contribute to the TRBEEC during the main phases, while in the recovery phases, the relativistic electrons contribute up to 80% of the TRBEEC. The results of the superposed epoch analysis of the solar wind parameters and geomagnetic indices indicate that the TRBEEC enhancement events prefe. . .
Date: 09/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2018JA025475 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JA025475
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