Found 1051 entries in the Bibliography.
Showing entries from 51 through 100
| 2020 |
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Radiation belt electron dropouts indicate electron flux decay to the background level during geomagnetic storms, which is commonly attributed to the effects of wave-induced pitch angle scattering and magnetopause shadowing. To investigate the loss mechanisms of radiation belt electron dropouts triggered by a solar wind dynamic pressure pulse event on 12 September 2014, we comprehensively analyzed the particle and wave measurements from Van Allen Probes. The dropout event was divided into three periods: before the storm, the ... Ma, Xin; Xiang, Zheng; Ni, Binbin; Fu, Song; Cao, Xing; Hua, Man; Guo, DeYu; Guo, YingJie; Gu, Xudong; Liu, ZeYuan; Zhu, Qi; YEAR: 2020 DOI: https://doi.org/10.26464/epp2020060 radiation belt electron flux dropouts; Geomagnetic storm; electron phase space density; magnetopause shadowing; wave–particle interactions; Van Allen Probes |
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Alpha Transmitter Signal Reflection and Triggered Emissions Russian Alpha radio navigation system (RSDN-20) emits F1 = 11.9 kHz signals into the magnetosphere which propagate as whistler mode waves. Observed by waveform continuous burst mode from Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) on Van Allen Probes, a case is presented and featured with ducted propagation, multiple reflections, and triggered emissions. Both risers and fallers appear in the triggered emissions. We use a ray tracing method to demonstrate ducted propagation, which has a s ... Gu, Wenyao; Chen, Lunjin; Xia, Zhiyang; An, Xin; Horne, Richard; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL090165 VLF transmitter; ducted propagation; triggered emission; Van Allen Probes |
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On the Formation of Wedge-Like Ion Spectral Structures in the Nightside Inner Magnetosphere Recent observations in the nightside inner magnetosphere have identified a series of wedge-like spectral structures in the energy-time spectrograms of oxygen, helium, and hydrogen ion fluxes. Although the shapes and distributions of these structures have been characterized by case and statistical studies, their formation mechanism remains unclear. Here we utilize a particle tracing model to reproduce the wedge-like structures successively observed by the twin Van Allen Probes. The model suggests that these structures origina ... Zhou, Xu-Zhi; Ren, Jie; Yang, Fan; Yue, Chao; Zong, Qiu-Gang; Fu, Sui-Yan; Wang, Yongfu; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028420 wedge-like structure; inner magnetosphere; substorm injection; magnetospheric convection; ring current; magnetotail; Van Allen Probes |
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Simultaneously Formed Wedge-Like Structures of Different Ion Species Deep in the Inner Magnetosphere In this study, ion data from the Helium, Oxygen, Proton, and Electron (HOPE) spectrometers onboard Van Allen Probes reveal the existence of wedge-like structures of O+, He+, and H+ ions deep in the inner magnetosphere. The behaviors of the wedge-like structures in terms of temporal evolution, spatial distribution, upper energy limit, as well as dependence on solar wind and different geomagnetic indices are investigated from both event studies of several consecutive orbits on 3 February 2013 and the subsequent statistical ana ... Ren, Jie; Zong, Q.; Yue, C.; Zhou, X.; . Y. Fu, S; Spence, H.; Funsten, H.; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028192 wedge-like structures; Ring current ions; inner magnetosphere; Substorm Injections; Van Allen Probes |
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Formation of the Low-Energy “Finger” Ion Spectral Structure Near the Inner Edge of the Plasma Sheet We present a case study of the H+, He+, and O+ low-energy “finger” structure observed by the Van Allen Probe A Helium, Oxygen, Proton, and Electron (HOPE) spectrometer on 26 October 2016. This structure, whose characteristic energy is from approximately tens of eV to a few keV, looks like a “finger” that is rich in O+ and He+, faint in H+ on an energy-time spectrogram. By using the Space Weather Modeling Framework (SWMF) and Weimer05 electric fields, combined with a dipole or more self-consistent magnetohydrodynamic ... Wang, Y.; Kistler, L.; Mouikis, C.; Zhang, J.; Lu, J; Welling, D.; Rastaetter, L.; Bingham, S.; Jin, Y.; Wang, L.; Miyoshi, Y.; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL089875 |
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Relation Between Shock-Related Impulse and Subsequent ULF Wave in the Earth s Magnetosphere The generation of Pc4-5 ultralow frequency (ULF) waves after interplanetary shock-induced electric field impulses in the Earth s magnetosphere is studied using Van Allen Probes measurements by investigating the relationship between the first impulses and subsequent resonant ULF waves. In the dayside, the relevant time scales of the first impulse is correlated better with local Alfvén speed than with local eigenfrequency, implying that the temporal scale of the first impulse is more likely related to fast-mode wave propagati ... Zhang, Dianjun; Liu, Wenlong; Li, Xinlin; Sarris, Theodore; Wang, Yongfu; Xiao, Chao; Zhang, Zhao; Wygant, John; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL090027 ULF wave; interplanetary shock; Magnetosphere; Field line resonance; electric field; wave excitation; Van Allen Probes |
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On 31 January 2016, the flux of >2 MeV electrons observed by Geostationary Operational Environmental Satellite (GOES)-13 dropped to the background level during a minor storm main phase (−48 nT). Then, a second storm (−53 nT) occurred on 2 February; during the 3 days after its main phase, the flux remained at background level. Using data from various instruments on the GOES, Polar Operational Environmental Satellites (POES), Radiation Belt Storm Probes (RBSP), Meteor-M2, and Fengyun-series spacecraft, we study this long ... Wu, H.; Chen, T.; Kalegaev, V.; Panasyuk, M.; Vlasova, N.; Duan, S.; Zhang, X.; He, Z.; Luo, J.; Wang, C.; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028098 Radiation belt; relativistic electron dropout; Geomagnetic storm; Van Allen Probes |
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Precipitation Loss of Radiation Belt Electrons by Two-Band Plasmaspheric Hiss Waves A two-band plasmaspheric hiss consisting of a low-frequency band (normal hiss with the frequency below 2 kHz) and a high-frequency band (locally generated hiss with the frequency up to 10 kHz) was observed on 6 January 2014 by the Van Allen Probes (He et al., 2019, https://doi.org/10.1029/2018GL081578). The electron scattering effect driven by this kind of two-band plasmaspheric hiss is evaluated by the quasi-linear diffusion simulation for the first time. Realistic wave characteristic parameters of the two-band plasmasp ... He, Zhaoguo; Yan, Qi; Zhang, Xiaoping; Yu, Jiang; Ma, Yonghui; Cao, Yong; Cui, Jun; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028157 two-band hiss; radiation belt electron; loss; Van Allen Probes |
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A New Approach to Constructing Models of Electron Diffusion by EMIC Waves in the Radiation Belts Electromagnetic ion cyclotron (EMIC) waves play an important role in relativistic electron losses in the radiation belts through diffusion via resonant wave-particle interactions. We present a new approach for calculating bounce and drift-averaged EMIC electron diffusion coefficients. We calculate bounce-averaged diffusion coefficients, using quasi-linear theory, for each individual Combined Release and Radiation Effects Satellite (CRRES) EMIC wave observation using fitted wave properties, the plasma density and the backgrou ... Ross, J.; Glauert, S.; Horne, R.; Watt, C.; Meredith, N.; Woodfield, E.; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL088976 Radiation belts; EMIC waves; electron diffusion; Van Allen Probes |
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Analytical Fast Magnetosonic Wave Model Based on Observations of Van Allen Probe Based on observations of Van Allen Probe-A during the period from 19 September 2012 to 28 February 2016, the relations of the fast magnetosonic (MS) wave amplitude Bw with kp index, the wave normal angle (WNA), and the wave normalized frequency (norF) are presented. Then, we establish an analytical regression model for MS wave amplitude as a function of geomagnetic storm activity (presented by kp index), L-shell (L), magnetic local time (MLT), magnetic latitude (λ), and the characteristics of MS wave, that is, wave norF and ... Yao, Fei; Yuan, Zhigang; Yu, Xiongdong; Wang, Dedong; Ouyang, Zhihai; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028527 fast magnetosonic wave; Van Allen Probe; analytical regression model; wave normal angle; Plasmapause; Van Allen Probes |
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Cross-Scale Quantification of Storm-Time Dayside Magnetospheric Magnetic Flux Content A clear understanding of storm-time magnetospheric dynamics is essential for a reliable storm forecasting capability. The dayside magnetospheric response to an interplanetary coronal mass ejection (ICME; dynamic pressure Pdyn > 20 nPa and storm-time index SYM-H < −150 nT) is investigated using in situ OMNI, Geotail, Cluster, MMS, GOES, Van Allen Probes, and THEMIS measurements. The dayside magnetic flux content is directly quantified from in situ magnetic field measurements at different radial distances. The arrival ... Akhavan-Tafti, M.; Fontaine, D.; Slavin, J.; Le Contel, O.; Turner, D.; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028027 interplanetary coronal mass ejection; magnetic flux quantification; cross-scale observations; flux transfer event; Dungey cycle; Geomagnetic storm; Van Allen Probes |
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Whistler mode chorus waves have recently been established as the most likely candidate for scattering relativistic electrons to produce the electron microbursts observed by low altitude satellites and balloons. These waves would have to propagate from the equatorial source region to significantly higher magnetic latitude in order to scatter electrons of these relativistic energies. This theoretically proposed propagation has never been directly observed. We present the first direct observations of the same discrete rising to ... Colpitts, Chris; Miyoshi, Yoshizumi; Kasahara, Yoshiya; Delzanno, Gian; Wygant, John; Cattell, Cynthia; Breneman, Aaron; Kletzing, Craig; Cunningham, Greg; Hikishima, Mitsuru; Matsuda, Shoya; Katoh, Yuto; Ripoll, Jean-Francois; Shinohara, Iku; Matsuoka, Ayako; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028315 Chorus; wave; propagation; Simultaneous observations; Radiation belt; Van Allen Probes |
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The local generation of high-frequency plasmaspheric hiss has recently been reported by a case study (He et al., 2019, https://doi.org/10.1029/2018GL081578). In this research, we perform statistics of global distributions of the locally generated high-frequency plasmaspheric hiss (LHFPH) for different levels of substorm activity, using 6-year observational data from Van Allen Probes. The statistics find that the LHFPH amplitude presents a strong magnetic local time (MLT) asymmetry and highly depends on substorm activity, and ... He, Zhaoguo; Yu, Jiang; Chen, Lunjin; Xia, Zhiyang; Wang, Wenrui; Li, Kun; Cui, Jun; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028526 |
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Substorm injection and solar wind dynamic pressure have long been considered as two main drivers of electromagnetic ion cyclotron (EMIC) wave excitation, but clear observational evidence is still lacking. With Van Allen Probes data from 2012–2017, we have investigated the roles of the two EMIC wave drivers separately, by using time-modified AE+ and . Both the occurrence rate and magnetic amplitude of waves significantly increase with the enhancement of each index. During large AE+, EMIC waves are mainly generated in the du ... Chen, Huayue; Gao, Xinliang; Lu, Quanming; Tsurutani, Bruce; Wang, Shui; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL090275 EMIC wave; wave excitation; source region; substorm injection; solar wind dynamic pressure; Earth s magnetosphere; Van Allen Probes |
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The k-nearest-neighbor technique is used to mine a multimission magnetometer database for a subset of data points from time intervals that are similar to the storm state of the magnetosphere for a particular moment in time. These subsets of data are then used to fit an empirical magnetic field model. Performing this for each snapshot in time reconstructs the dynamic evolution of the magnetic and electric current density distributions during storms. However, because weaker storms occur more frequently than stronger storms, th ... Stephens, G.; Bingham, S.; Sitnov, M.; Gkioulidou, M.; Merkin, V.; Korth, H.; Tsyganenko, N.; . Y. Ukhorskiy, A; YEAR: 2020 DOI: https://doi.org/10.1029/2020SW002583 storms; empirical geomagnetic field; ring current; data mining; eastward current; plasma pressure; Van Allen Probes |
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Energetic electron dynamics is highly affected by plasma waves through quasilinear and/or nonlinear interactions in the Earth s inner magnetosphere. In this letter, we provide physical explanations for a previously reported intriguing event from the Van Allen Probes observations, where bursts of electron butterfly distributions at tens of keV exhibit remarkable correlations with chorus waves. Both test particle and quasilinear simulations are used to reveal the formation mechanism for the bursts of electron butterfly distrib ... Gan, L.; Li, W.; Ma, Q.; Artemyev, A.; Albert, J.; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL090749 butterfly distribution; chorus waves; Electron acceleration; Radiation belts; nonlinear interaction; Van Allen Probes |
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Dynamic Properties of Particle Injections Inside Geosynchronous Orbit: A Multisatellite Case Study Four closely located satellites at and inside geosynchronous orbit (GEO) provided a great opportunity to study the dynamical evolution and spatial scale of premidnight energetic particle injections inside GEO during a moderate substorm on 23 December 2016. Just following the substorm onset, the four spacecraft, a LANL satellite at GEO, the two Van Allen Probes (also called “RBSP”) at ~5.8 RE, and a THEMIS satellite at ~5.3 RE, observed substorm-related particle injections and local dipolarizations near the central meridi ... Motoba, T.; Ohtani, S.; Claudepierre, S.; Reeves, G.; . Y. Ukhorskiy, A; Lanzerotti, L.; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028215 deep particle injections; dipolarizations; substorms; localized DF; Van Allen Probes |
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The Impenetrable Barrier: Suppression of Chorus Wave Growth by VLF Transmitters Rapid radiation belt recovery following storm time depletion involves local acceleration of multi-MeV electrons in nonlinear interactions with VLF chorus waves. Previous studies of an apparent impenetrable barrier at L ~ 2.8 focused on diffusion and precipitation loss mechanisms for an explanation of the sharp reduction of multi-MeV electron fluxes earthward of L ~ 3. Van Allen Probes observations for cases when the plasmasphere is contracted earthward of L ~ 3 indicate that strong coherent signals from VLF transmitter ... Foster, John; Erickson, Philip; Omura, Yoshiharu; Baker, Daniel; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA027913 Radiation belt; Plasmapause; VLF transmitters; wave-particle interactions; Electron acceleration; nonlinear VLF chorus; Van Allen Probes |
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Suprathermal electrons are a major heat source of ionospheric plasma. How the suprathermal electrons evolve during their bounces inside the plasmasphere is a fundamental question for the magnetosphere-ionosphere coupling. On the basis of Van Allen Probes observations and quasi-linear simulations, we present here the first quantitative study on the evolution of suprathermal electrons under the competition between Landau heating by whistler mode hiss waves and Coulomb collisional cooling by background plasma inside a plasmasph ... Wang, Zhongshan; Su, Zhenpeng; Liu, Nigang; Dai, Guyue; Zheng, Huinan; Wang, Yuming; Wang, Shui; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL089649 magnetosphere-ionosphere coupling; whistler mode hiss waves; Landau resonance; Coulomb collisions; suprathermal electrons; ring current; Van Allen Probes |
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Lower-Band “Monochromatic” Chorus Riser Subelement/Wave Packet Observations Three lower-band (f < 0.5 fce) chorus riser elements detected in the dayside generation region were studied in detail using the Van Allen Probe data. Two subelements/wave packets within each riser were examined for their wave “frequency” constancy within seven consecutive wave cycles. The seven wave cycles contained the maximum amplitudes of the subelements/packets. Maximum variance B1 zero crossings were used for the identification of wave cycle start and stop times. It is found that the frequency is constant to with ... Tsurutani, Bruce; Chen, Rui; Gao, Xinliang; Lu, Quanming; Pickett, Jolene; Lakhina, Gurbax; Sen, Abhijit; Hajra, Rajkumar; Park, Sang; Falkowski, Barbara; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028090 chorus coherency; chorus subelement monochromaticity; a modified theory needed; Van Allen Probes |
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In this study we investigate two distinct loss mechanisms responsible for the rapid dropouts of radiation belt electrons by assimilating data from Van Allen Probes A and B and Geostationary Operational Environmental Satellites (GOES) 13 and 15 into a 3-D diffusion model. In particular, we examine the respective contribution of electromagnetic ion cyclotron (EMIC) wave scattering and magnetopause shadowing for values of the first adiabatic invariant μ ranging from 300 to 3,000 MeV G−1. We inspect the innovation vector ... Cervantes, S.; . Y. Shprits, Y; Aseev, N.; Allison, H.; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028208 data assimilation; EMIC waves; magnetopause shadowing; innovation vector; Kalman Filter; radiation belt losses; Van Allen Probes |
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Evidence of Nonlinear Interactions Between Magnetospheric Electron Cyclotron Harmonic Waves Electron cyclotron harmonic (ECH) waves play an important role in the magnetosphere-ionosphere coupling. They are usually considered to be generated by the Bernstein-mode instability with electron loss cone distributions. By analyzing the Van Allen Probes wave data, we present the direct evidence of the nonlinear interactions between ECH waves in the magnetosphere. Substorm-injected electrons excite primary ECH waves in a series of structureless bands between multiples of the electron gyrofrequency. Nonlinear interactions be ... Gao, Zhonglei; Zuo, Pingbing; Feng, Xueshang; Wang, Yi; Jiang, Chaowei; Wei, Fengsi; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL088452 ECH; wave-wave interaction; nonlinear interaction; frequency spectrum broadening; electron Bernstein mode; generalized Bernstein mode; Van Allen Probes |
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Ionospheric Signatures of Ring Current Ions Scattered by Magnetosonic Waves In this letter, we present unique conjugated satellite observations of ionospheric signatures of ring current (RC) ions scattered by fast magnetosonic (MS) waves. In the plasmasphere, the Van Allen Probe in situ observed MS waves. At ionospheric altitudes, the NOAA 16 satellite at the footprint of Van Allen Probe simultaneously observed obvious enhancements of mirroring RC ions, but no obvious variations of precipitating RC ions at subauroral latitudes. Theoretical calculations of pitch angle diffusion coefficients for RC io ... Yuan, Zhigang; Yao, Fei; Yu, Xiongdong; Ouyang, Zhihai; Huang, Shiyong; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL089032 magnetosonic waves; mirroring ions; pitch angle scatter; precipitating ions; Van Allen Probes; Ring current ions |
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The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) mission provided long-term measurements of 10s of megaelectron volt (MeV) inner belt (L < 2) protons (1992–2009) as did the Polar-orbiting Operational Environmental Satellite-18 (POES-18, 2005 to present). These long-term measurements at low-Earth orbit (LEO) showed clear solar cycle variations which anticorrelate with sunspot number. However, the magnitude of the variation is much greater than the solar cycle variation of galactic cosmic rays (>GeV) tha ... Li, Xinlin; Xiang, Zheng; Zhang, Kun; Khoo, Lengying; Zhao, Hong; Baker, Daniel; Temerin, Michael; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028198 Inner radiation belt; Inner Belt Proton; Solar cycle variation; Cosmic rays; neutron monitor; Low Earth Orbit satellite; Van Allen Probes |
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Earth s slot region, lying between the outer and inner radiation belts, has been identified as due to a balance between inward radial diffusion and pitch angle (PA) scattering induced by waves. However, recent satellite observations and modeling studies indicate that cosmic ray albedo neutron decay (CRAND) may also play a significant role in energetic electron dynamics in the slot region. In this study, using a drift-diffusion-source model, we investigate the relative contribution of all significant waves and CRAND to the dy ... Xiang, Zheng; Li, Xinlin; Ni, Binbin; Temerin, M.; Zhao, Hong; Zhang, Kun; Khoo, Leng; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028042 Slot region; Wave-particle interaction; CRAND; energetic electrons; Van Allen Probes |
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Recent availability of a considerable amount of satellite and ground-based data has allowed us to analyze rare conjugated events where extremely low and very low frequency waves from the same source region are observed in different locations. Here, we report a quasiperiodic (QP) emission, showing one-to-one correspondence, observed by three satellites in space (Arase and the Van Allen Probes) and a ground station. The main event was on 29 November 2018 from 12:06 to 13:08 UT during geomagnetically quiet times. Using the po ... Martinez-Calderon, C.; Němec, F.; Katoh, Y.; Shiokawa, K.; Kletzing, C.; Hospodarsky, G.; Santolik, O.; Kasahara, Y.; Matsuda, S.; Kumamoto, A.; Tsuchiya, F.; Matsuoka, A.; Shoji, M.; Teramoto, M.; Kurita, S.; Miyoshi, Y.; Ozaki, M.; Nishitani, N.; Oinats, A.; Kurkin, V.; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028126 VLF/ELF; spatial extent; conjugated events; ERG; RBSP; quasiperiodic emissions; Van Allen Probes |
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Lightning generated whistlers (LGWs) play an important role in precipitating energetic electrons in the Earth s inner radiation belt and beyond. Wave burst data from the Van Allen Probes are used to unambiguously identify LGWs and analyze their properties at L < 4 by extending their frequencies down to ~100 Hz for the first time. The statistical results show that LGWs typically occur at frequencies from 100 Hz to 10 kHz with the major wave power below the equatorial lower hybrid resonance frequency, and their wave ampli ... Green, A.; Li, W.; Ma, Q.; Shen, X.-C.; Bortnik, J.; Hospodarsky, G.; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL089584 lightning generated whistlers; electron precipitation; Inner radiation belt; hiss; VLF transmitter waves; global distribution; Van Allen Probes |
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Using measurements from the Van Allen Probes, we show that field-aligned fluxes of electrons energized by dispersive Alfvén waves (DAWs) are prominent in the inner magnetosphere during active conditions. These electrons have preferentially field-aligned anisotropies from 1.2 to >2 at energies ranging from tens of electron volts to several kiloelectron volts (keV), with largest values being coincident with magnetic field dipolarizations. Comparisons reveal that DAW energy densities and Poynting fluxes are strongly correlated ... Hull, A.; Chaston, C.; Bonnell, J.; Damiano, P.; Wygant, J.; Reeves, G.; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL088985 dispersive Alfvén waves; field-aligned electrons; inner magnetosphere; oxygen ion outflow; Geomagnetic storms; substorms; Van Allen Probes |
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In this study, we performed a series of long-term and individual storm simulations with and without hiss, chorus, and electromagnetic ion cyclotron (EMIC) waves. We compared simulation results incorporating different wave modes with Van Allen Probes flux observations to illustrate how hiss and chorus waves aid EMIC waves in depleting multi-MeV electrons. We found that EMIC, hiss, and chorus waves are required to reproduce satellite measurements in our simulations. Our results indicate that hiss waves play a dominant role in ... . Y. Drozdov, A; Usanova, M.; Hudson, M.; Allison, H.; . Y. Shprits, Y; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028282 EMIC waves; Radiation belts; Whistler waves; VERB code; Fokker-Planck diffusion equation; Van Allen Probes |
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Electromagnetic ion cyclotron (EMIC) waves play an important role in the energy transfer among particles of different energies and species in the magnetosphere, whose drivers have been commonly recognized as solar wind compressions and storm/substorm proton injections. However, how the solar wind decompressions related to frequently occurring discontinuities compete with the proton injections in the evolution of EMIC waves has been rarely investigated. Here we present a complete end-to-end observation by Wind, THEMIS, and Va ... Liu, Nigang; Su, Zhenpeng; Gao, Zhonglei; Zheng, Huinan; Wang, Yuming; Wang, Shui; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL090296 EMIC waves; solar wind discontinuity; storm/substorm injection; wave generation; adiabatic deceleration; inner magnetosphere; Van Allen Probes |
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Whistler mode chorus waves can scatter plasma sheet electrons into the loss cone and produce the Earth s diffuse aurora. Van Allen Probes observed plasma sheet electron injections and intense chorus waves on 24 November 2012. We use quasilinear theory to calculate the precipitating electron fluxes, demonstrating that the chorus waves could lead to high differential energy fluxes of precipitating electrons with characteristic energies of 10–30 keV. Using this method, we calculate the precipitating electron flux from 2012 t ... Ma, Q.; Connor, H.; Zhang, X.-J.; Li, W.; Shen, X.-C.; Gillespie, D.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Claudepierre, S.; Reeves, G.; Spence, H.; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL088798 Chorus wave; electron precipitation; plasma sheet electron; Van Allen Probes observation; Van Allen Probes |
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Origin of Electron Boomerang Stripes: Localized ULF Wave-Particle Interactions Ultralow frequency (ULF) wave-particle interactions play a significant role in the radiation belt dynamic process, during which drift resonance can accelerate and transport energetic electrons in the outer radiation belt. Observations of wave-electron drift resonance are characterized by quasiperiodic straight or “boomerang-shaped” stripes in the pitch angle spectrogram. Here we present an ULF wave event on 1 December 2015, during which both kinds stripes were observed by Van Allen Probes A and B, respectively. Using the ... Zhao, X.; Hao, Y.; Zong, Q.-G.; Zhou, X.-Z.; Yue, Chao; Chen, X.; Liu, Y.; Blake, J.; Claudepierre, S.; Reeves, G.; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL087960 boomerang-shaped stripes; ULF waves; drift resonance; time of flight; Van Allen Probes |
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The background cold electron density plays an important role in plasma and wave dynamics. Here, we investigate an event with clear modulation of the particle fluxes and wave intensities by background electron density irregularities based on Van Allen Probes observations. The energies at the peak fluxes of protons and Helium ions of 100 eV to several keV are well correlated with the total electron density variation. Intense electromagnetic ion cyclotron (EMIC) and magnetosonic (MS) waves are simultaneously observed in the hi ... Yue, Chao; Ma, Qianli; Jun, Chae-Woo; Bortnik, Jacob; Zong, Qiugang; Zhou, Xuzhi; Jang, Eunjin; Reeves, Geoffrey; Spence, Harlan; Wygant, John; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL088855 electron density irregularities; electromagnetic ion cyclotron; magnetosonic waves; suprathermal particles; Wave-particle interaction; wave growth rate; Van Allen Probes |
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We report a rare event of intense plasmaspheric hiss and chorus waves simultaneously observed at the same L shell but different magnetic local times by Van Allen Probes and Magnetospheric Multiscale. Based on the measured waves and electron distributions, we calculate the bounce-averaged diffusion coefficients and subsequently simulate the temporal evolution of electron distributions. The simulations show that the dynamics of tens to hundreds of keV electrons are jointly controlled by hiss and chorus. The dynamics of MeV ele ... Yu, J.; Wang, J.; . Y. Li, L; Cui, J.; Cao, J.; He, Z.; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL088753 electron diffusion; Plasmaspheric Hiss; chorus waves; Van Allen Probes; MMS |
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The flux of energetic electrons in the outer radiation belt shows a high variability. The interactions of electrons with very low frequency (VLF) chorus waves play a significant role in controlling the flux variation of these particles. Quantifying the effects of these interactions is crucially important for accurately modeling the global dynamics of the outer radiation belt and to provide a comprehensive description of electron flux variations over a wide energy range (from the source population of 30 keV electrons up to th ... Aryan, Homayon; Agapitov, Oleksiy; Artemyev, Anton; Mourenas, Didier; Balikhin, Michael; Boynton, Richard; Bortnik, Jacob; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028018 electron lifetimes; Van Allen radiation belts; chorus waves; pitch angle diffusion coefficients; Van Allen Probes; Cluster |
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In this study we focus on the radiation belt dynamics driven by the geomagnetic storms during September 2017. Besides the long-lasting three-belt structures of ultrarelativistic electrons (>2 MeV, existing for tens of days), which has been studied intensively during the Van Allen Probe era, it is found that magnetospheric electrons of hundreds of keVs can also have three-belt structures at similar L extent during storm time. Measurements of 500–800 keV electrons from MagEIS instrument onboard Van Allen Probes show double- ... Hao, Y.; Zong, Q.-G.; Zhou, X.-Z.; Zou, H.; Rankin, R.; Sun, Y.; Chen, X.; Liu, Y.; . Y. Fu, S; Baker, D.; Spence, H.; Blake, J.; Reeves, G.; Claudepierre, S.; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028031 storage ring; three-belt structure; hiss wave; electron lifetime; Radial Transport; Van Allen Probes |
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Calculation of the Atomic Oxygen Fluence on the Van Allen Probes The Van Allen Probes Mission consists of two identical spacecraft flying in highly elliptical orbits, with perigee altitudes originally near 600 km. During the low-altitude periods of the orbits, the spacecrafts are immersed in a region of high-density atomic oxygen. Atomic oxygen is known to change and degrade the properties of spacecraft surfaces (Banks et al., 2004), such as those of the Van Allen Probes Electric Field and Waves (EFW) instrument. The consistency of the sensor surfaces in EFW is important because the me ... Schumm, G.; Bonnell, J.; Wygant, J.; Mozer, F.; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA027944 |
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In this study, a magnetic dip event in which a small-scale magnetic dip is embedded within a large-scale magnetic dip is analyzed based on the observations of the Van Allen Probes. The small-scale dip is contributed by a sharp electron injection at the energy range of 1 to 10 keV, but the large-scale dip is contributed by a smooth proton injection at the energy range higher than 10 keV. The formation of dip caused by the suprathermal electrons is supported by the self-consistent magnetic model. Moreover, the echoes of bu ... Zhu, Hui; Chen, Lunjin; Xia, Zhiyang; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL088983 magnetic dips; echoes of butterfly distributions; ring current-radiation belt coupling; Van Allen Probes |
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Using wave measurements from the EMFISIS instrument onboard Van Allen Probes, we investigate statistically the spatial distributions of the intensity of plasmaspheric hiss waves. To reproduce these empirical results, we establish a fitting model that is a third-order polynomial function of L-shell, magnetic local time (MLT), magnetic latitude (MLAT), and AE*. Quantitative comparisons indicate that the model s fitting functions can reflect favorably the major empirical features of the global distribution of hiss wave intensit ... Wang, JingZhi; Zhu, Qi; Gu, Xudong; Fu, Song; Guo, JianGuang; Zhang, Xiaoxin; Yi, Juan; Guo, YingJie; Ni, Binbin; Xiang, Zheng; YEAR: 2020 DOI: https://doi.org/10.26464/epp2020034 |
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The “zebra stripes” are peaks and valleys commonly present in the spectrograms of energetic particles trapped in the Earth s inner belt and slot region. Several theories have been proposed over the years to explain their generation, structure, and evolution. Yet, the plausibility of various theories has not been tested due to a historical lack of ground truth, including in situ electric field measurements. In this work, we leverage the new visibility offered by the database of Van Allen Probes electric drift measurements ... Lejosne, Solène; Mozer, Forrest; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA027889 zebra stripes; superposed epoch analysis; prompt penetration electric fields; Inner radiation belt; substorm; Van Allen Probes |
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Defining Radiation Belt Enhancement Events Based on Probability Distributions We present a methodology to define moderate, strong, and intense space weather events based on probability distributions. We have illustrated this methodology using a long-duration, uniform data set of 1.8–3.5 MeV electron fluxes from multiple LANL geosynchronous satellite instruments, but a strength of this methodology is that it can be applied uniformly to heterogeneous data sets. It allows quantitative comparison of data sets with different energies, units, orbits, and so forth. The methodology identifies a range of ti ... Reeves, Geoffrey; Vandegriff, Elizabeth; Niehof, Jonathan; Morley, Steven; Cunningham, Gregory; Henderson, Michael; Larsen, Brian; YEAR: 2020 DOI: https://doi.org/10.1029/2020SW002528 Radiation belts; methods; geosynchronous; energetic particles; hazards; Solar Cycle; Van Allen Probes |
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Simulations of Electron Flux Oscillations as Observed by MagEIS in Response to Broadband ULF Waves Coherent electron flux oscillations of hundreds of keV are often observed by the Van Allen Probes in the magnetosphere during quiet times in association with ultralow frequency (ULF) waves. They are observed in the form of periodic flux fluctuations, with a drift frequency that is energy dependent, but are not associated with drift echoes following storm- or substorm-related energetic particle injections. Instead, they are associated with the resonant interaction of electrons with ULF waves and are an indication of ongoing e ... Sarris, Theodore; Li, Xinlin; Temerin, Michael; Zhao, Hong; Khoo, Leng; Turner, Drew; Liu, Wenlong; Claudepierre, Seth; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA027798 electron flux oscillations; ULF waves; Magnetosphere; Radiation belts; radial diffusion; particle tracing simulations; Van Allen Probes |
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Whistler mode waves observed in the Earth s inner magnetosphere at frequencies between about 0.5 and 4 kHz which exhibit a nearly periodic time modulation of the wave intensity are called quasiperiodic (QP) emissions. Conjugate measurements of QP events at several different locations can be used to estimate their spatial extent and spatiotemporal variability. Results obtained using conjugate QP measurements provided by the ground-based station Kannuslehto (L≈5.5) and the Van Allen Probes spacecraft (L shells between about ... Bezděková, B.; Němec, F.; Manninen, J.; Hospodarsky, G.; Santolik, O.; Kurth, W.; Hartley, D.; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA027793 |
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Solar Energetic Proton Access to the Near-Equatorial Inner Magnetosphere In this study we examine the ability of protons of solar origin to access the near-equatorial inner magnetosphere. Here we examine four distinct solar proton events from 20–200 MeV, concurrent with both quiet time and storm time conditions using proton data from the ACE satellite in the solar wind upstream of Earth and data from the Relativistic Electron Proton Telescope (REPT) instrument aboard Van Allen Probes. We examine the direct flux correspondence between interplanetary space and the inner magnetosphere. Small subs ... Filwett, Rachael; Jaynes, Allison; Baker, Daniel; Kanekal, Shrikanth; Kress, Brian; Blake, Bern; YEAR: 2020 DOI: https://doi.org/10.1029/2019JA027584 |
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Global Model of Whistler Mode Chorus in the Near-Equatorial Region (|λm|< 18°) We extend our database of whistler mode chorus, based on data from seven satellites, by including ∼3 years of data from Radiation Belt Storm Probes (RBSP)-A and RBSP-B and an additional ∼6 years of data from Time History of Events and Macroscale Interactions during Substorms (THEMIS)-A, THEMIS-D, and THEMIS-E. The new database allows us to probe the near-equatorial region in detail, revealing new features. In the equatorial source region, |λm|<6°, strong wave power is most extensive in the 0.1–0.4fce bands in the r ... Meredith, Nigel; Horne, Richard; Shen, Xiao-Chen; Li, Wen; Bortnik, Jacob; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL087311 whistler mode chorus; wave-particle interactions; Radiation belts; Van Allen Probes |
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Whistler-mode hiss waves generally determine MeV electron lifetimes inside the plasmasphere. We use Van Allen Probes measurements to provide the first comprehensive statistical survey of plasmaspheric hiss-driven quasi-linear pitch-angle diffusion rates and lifetimes of MeV electrons as a function of L*, local time, and AE index, taking into account hiss power, electron plasma frequency to gyrofrequency ratio ωpe/Ωce, hiss frequency at peak power ωm, and cross correlations of these parameters. We find that during geomagne ... Agapitov, O.; Mourenas, D.; Artemyev, A.; Claudepierre, S.; Hospodarsky, G.; Bonnell, J.; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL088052 electron lifetimes; plasmasphere; hiss waves; wave-particle interactions; Van Allen Probes |
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Simultaneous Observations of Localized and Global Drift Resonance In this study, we present Van Allen Probe observations showing that seed (hundreds of keV) and core ( 1 MeV) electrons can resonate with ultra-low-frequency (ULF) wave modes with distinctive m values simultaneously. An unusual electron energy spectrogram with double-banded resonant structure was recorded by energetic particle, composition, and thermal plasma (ECT)-magnetic electron ion spectrometer (MagEIS) and, meanwhile, boomerang stripes in pitch angle spectrogram appeared at the lower energy band. A localized drift reson ... Hao, Y.; Zhao, X.; Zong, Q.-G.; Zhou, X.-Z.; Rankin, R.; Chen, X.; Liu, Y.; . Y. Fu, S; Blake, J.; Reeves, G.; Claudepierre, S.; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL088019 drift resonance; ULF waves; Radiation Belt Dynamics; boomerang stripes; azimuthal wave number; multiple resonances; Van Allen Probes |
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Global ENA Imaging and In Situ Observations of Substorm Dipolarization on 10 August 2016 Abstract This paper presents the first combined use of data from Magnetospheric Multiscale (MMS), Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS), and Van Allen Probes (RBSP) to study the 10 August 2016 magnetic dipolarization. We report the first correlation of MMS tail observations with TWINS energetic neutral atom (ENA) images of the ring current (RC). We analyze 15-min, 1° TWINS 2 images in 1–50 keV energy bins. To characterize the high-altitude RC we extract peak ENA flux from L= 2.5 to 5 in the postmid ... Goldstein, J.; Valek, P.; McComas, D.; Redfern, J.; Spence, H.; Skoug, R.; Larsen, B.; Reeves, G.; Nakamura, R.; YEAR: 2020 DOI: 10.1029/2019JA027733 substorm dipolarization; cross-scale physics; imaging; multipoint in situ; ring current; Van Allen Probes |
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Abstract On 22 December 2015, the two Van Allen Probes observed two sets of electromagnetic ion cyclotron (EMIC) wave bursts during a close conjunction when both Probe A and Probe B were separated by 0.57 to 0.68 RE. The EMIC waves occurred during an active period in the recovery phase of a coronal mass ejection-driven geomagnetic storm. Both spacecraft observed EMIC wave bursts that had similar spatial structure within a 1–2 min time delay. The EMIC waves occurred outside the plasmasphere, within ΔL ≈ 1–2 of the ... Sigsbee, K.; Kletzing, C. A.; Faden, J.; Jaynes, A. N.; Reeves, G.; Jahn, J.-M.; YEAR: 2020 DOI: 10.1029/2019JA027424 EMIC waves; Plasmapause; Proton Anisotropy; Storm Recovery Phase; Van Allen Probes; pitch angle scattering |
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Abstract A comprehensive numerical raytracing study of whistler mode wave power with the inclusion of finite background electron and ion temperature is performed in order to investigate wave power distribution in relation to the plasmapause. Both Landau damping and linear growth of whistler mode waves are taken into account using a bi-Maxwellian hot electron distribution as well as an isotropic hot electron distribution. Isotropic and bi-Maxwellian distributions yield similar results of statistical spatial wave power for fre ... Maxworth, A.; Gołkowski, M.; Malaspina, D.; Jaynes, A.; YEAR: 2020 DOI: 10.1029/2019JA027154 hiss; plasmasphere; Warm Plasma; Raytracing; Magnetosphere; Van Allen Probes |
