Found 59 entries in the Bibliography.
Showing entries from 1 through 50
| 2021 |
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Fast magnetosonic (MS) waves are excited by the ring distribution of energetic protons preferably when the ring velocity (VR) is within a factor of 2 above or below the local Alfvén speed (VA). Here we examine the global distributions of MS waves and proton rings with 0.5VA ≤ VR ≤ 2VA based on 64 months (from October 25, 2012 to February 28, 2018) of Van Allen Probes observations. The statistical results show that MS waves are present over a broad region of L = 1.2–6.0 and 00–24 magnetic local time (MLT), wit ... Zhou, Qinghua; Jiang, Zheng; Yang, Chang; He, Yihua; Liu, Si; Xiao, Fuliang; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028354 Fast Magnetosonic Waves; global occurrences; proton ring distribution; Radiation belt; Van Allen Probe observation; Van Allen Probes |
| 2020 |
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Statistical Study of Chorus Modulations by Background Magnetic Field and Plasma Density In this study, we use observations of THEMIS and Van Allen Probes to statistically study the modulations of chorus emissions by variations of background magnetic field and plasma density in the ultra low frequency range. The modulation events are identified automatically and divided into three types according to whether the chorus intensity correlates to the variations of the magnetic field only (Type B), plasma density only (Type N), or both (Type NB). For the THEMIS observations, the occurrences of the Types B and N are la ... Xia, Zhiyang; Chen, Lunjin; Li, Wen; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL089344 |
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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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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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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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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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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 Relation Between Electron Cyclotron Harmonic Waves and Plasmapause: Case and Statistical Studies Abstract Observationally, electron cyclotron harmonic (ECH) waves are often terminated at the outer boundary of the plasmasphere boundary layer (PBL, i.e., plasmapause). Physics of this empirical relation is not well established. In this study, two categories of ECH waves are shown by their different behaviors near PBL. For Category I, all bands of ECH waves terminate at PBL because the density ratio (nh/nc) between hot and cold electrons decreases dramatically across PBL. For Category II, ECH waves, especially the lower har ... Liu, Xu; Chen, Lunjin; Xia, Zhiyang; YEAR: 2020 DOI: 10.1029/2020GL087365 two types of ECH wave; Plasmapause; instability; excitation and attenuation mechanism; statistical characteristics of two types of ECH wave; Van Allen Probes |
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The Relation Between Electron Cyclotron Harmonic Waves and Plasmapause: Case and Statistical Studies Observationally, electron cyclotron harmonic (ECH) waves are often terminated at the outer boundary of the plasmasphere boundary layer (PBL, i.e., plasmapause). Physics of this empirical relation is not well established. In this study, two categories of ECH waves are shown by their different behaviors near PBL. For Category I, all bands of ECH waves terminate at PBL because the density ratio (nh/nc) between hot and cold electrons decreases dramatically across PBL. For Category II, ECH waves, especially the lower harmonic ban ... Liu, Xu; Chen, Lunjin; Xia, Zhiyang; YEAR: 2020 DOI: https://doi.org/10.1029/2020GL087365 two types of ECH wave; Plasmapause; instability; excitation and attenuation mechanism; statistical characteristics of two types of ECH wave; Van Allen Probes |
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Upper Limit of Electron Fluxes Observed in the Radiation Belts Radiation belt electrons have a complicated relationship with geomagnetic activity. We select electron measurements from 7 years of DEMETER and 6 years of Van Allen Probes data during geomagnetic storms to conduct statistical analysis focusing on the correlation between electron flux and Dst index. We report, for the first time, an upper limit of electron fluxes observed by both satellites throughout the inner and outer belts across a wide energy range from ?100s keV to multi-MeV. The upper flux limit is determined at diffe ... Zhang, Kun; Li, Xinlin; Zhao, Hong; Xiang, Zheng; Khoo, Leng; Zhang, Wenxun; Hogan, Benjamin; Temerin, Michael; YEAR: 2020 DOI: https://doi.org/10.1029/2020JA028511 electron; Radiation belt; statistics; upper limit; Van Allen Probes |
| 2019 |
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In this report, the relationship between innermost plasmapause locations (Lpp) and initial electron enhancements during both storm and nonstorm (Dst > -30 nT) periods are examined using data from the Van Allen Probes. The geomagnetic storms are classified into coronal mass ejection (CME)-driven and corotating interaction region (CIR)-driven storms to explore their influences on the initial electron enhancements, respectively. We also study nonstorm time electron enhancements and observe frequent, sudden (within two consecuti ... Khoo, L.-Y.; Li, X.; Zhao, H.; Chu, X.; Xiang, Z.; Zhang, K.; YEAR: 2019 DOI: 10.1029/2019JA027412 energetic electron enhancements; Plasmapause; Radiation Belt Dynamics; Van Allen Probes |
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Auroral kilometric radiation (AKR) can potentially produce serious damage to space-borne systems by accelerating trapped radiation belt electrons to relativistic energies. Here we examine the global occurrences of AKR emissions in radiation belts based on Van Allen Probes observations from 1 October 2012 to 31 December 2016. The statistical results (1,848 events in total) show that AKR covers a broad region of L= 3\textendash6.5 and 00\textendash24 magnetic local time (MLT), with a higher occurrence on the nightside (20\text ... Zhao, Wanli; Liu, Si; Zhang, Sai; Zhou, Qinghua; Yang, Chang; He, Yihua; Gao, Zhonglei; Xiao, Fuliang; YEAR: 2019 DOI: 10.1029/2019GL083944 Auroral kilometric radiation; global occurrence; Radiation belt; suprathermal electron flux enhancenments; Van Allen Probes |
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Whistler mode hiss acts as an important loss mechanism contributing to the radiation belt electron dynamics inside the plasmasphere and plasmaspheric plumes. Based on Van Allen Probes observations from September 2012 to December 2015, we conduct a detailed analysis of hiss properties in plasmaspheric plumes and illustrate that corresponding to the highest occurrence probability of plumes at L = 5.0\textendash6.0 and MLT = 18\textendash21, hiss emissions occur concurrently with a rate of >~80\%. Plume hiss can efficiently sca ... Zhang, Wenxun; Ni, Binbin; Huang, He; Summers, Danny; Fu, Song; Xiang, Zheng; Gu, Xudong; Cao, Xing; Lou, Yuequn; Hua, Man; YEAR: 2019 DOI: 10.1029/2018GL081863 Electron scattering; plasmaspheric plumes; plume hiss; Van Allen Probes |
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Electrostatic electron cyclotron harmonic (ECH) waves can yield diffuse aurora primarily at higher L-shells by driving efficient precipitation loss of plasma sheet electrons. Here using the Van Allen Probes high resolution data, we examine in detail the global occurrences of ECH waves during the period from October 1, 2012 to June 30, 2017 and find that there are totally 419 events of enhanced ECH waves. The statistical results demonstrate that ECH waves can be present over a broad region of L=4-6 and 00-24 MLT, with a highe ... Chen, Yaru; Zhou, Qinghua; He, Yihua; Yang, Chang; Liu, Si; Gao, Zhonglei; Xiao, Fuliang; YEAR: 2019 DOI: 10.1029/2019GL082668 electron ring distribution; global occurrences; Radiation belt; Van Allen Probe observation; Van Allen Probes; waves |
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We report on evidence for the generation of an ultra-low frequency plasma wave by the drift-mirror plasma instability in the dynamic plasma environment of Earth\textquoterights inner magnetosphere. The plasma measurements are obtained from the Radiation Belt Storm Probes Ion Composition Experiment onboard NASA\textquoterights Van Allen Probes Satellites. We show that the measured wave-particle interactions are driven by the drift-mirror instability. Theoretical analysis of the data demonstrates that the drift-mirror mode pla ... Soto-Chavez, A.; Lanzerotti, L.; Manweiler, J.; Gerrard, A.; Cohen, R.; Xia, Z.; Chen, L.; Kim, H.; YEAR: 2019 DOI: 10.1063/1.5083629 |
| 2018 |
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Electromagnetic whistler-mode chorus and electrostatic electron cyclotron harmonic (ECH) waves can contribute significantly to auroral electron precipitation and radiation belt electron acceleration. In the past, linear and nonlinear wave-particle interactions have been proposed to explain the occurrences of these magnetospheric waves. By analyzing Van Allen Probes data, we present here the first evidence for nonlinear coupling between chorus and ECH waves. The sum-frequency and difference-frequency interactions produced the ... Gao, Zhonglei; Su, Zhenpeng; Xiao, Fuliang; Summers, Danny; Liu, Nigang; Zheng, Huinan; Wang, Yuming; Wei, Fengsi; Wang, Shui; YEAR: 2018 DOI: 10.1029/2018GL080635 aurora; Chorus wave; electron cyclotron harmonic wave; nonlinear wave-wave interaction; Radiation belt; Van Allen Probes |
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Using Van Allen Probes\textquoteright observations and established plasmapause location (Lpp) models, we investigate the relationship between the location of the initial enhancement (IE) of energetic electrons and the innermost (among all magnetic local time sectors) Lpp over five intense storm periods. Our study reveals that the IE events for 30 keV to 2MeV electrons always occurred outside of the innermost Lpp. On average, the inner extent of the IE events (LIE) for <800 keV electrons was closer to the innermost Lpp when c ... Khoo, Leng; Li, Xinlin; Zhao, Hong; Sarris, Theodore; Xiang, Zheng; Zhang, Kun; Kellerman, Adam; Blake, Bernard; YEAR: 2018 DOI: 10.1029/2018JA026074 energetic electron; enhancements; plasmasphere; Radiation belt; Van Allen Probes |
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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 w ... Hua, Man; Ni, Binbin; Fu, Song; Gu, Xudong; Xiang, Zheng; Cao, Xing; Zhang, Wenxun; He, Ying; Huang, He; Lou, Yuequn; Zhang, Yang; YEAR: 2018 DOI: 10.1029/2018GL079533 Combined scattering effect; diffusion simulations; Exohiss; magnetosonic waves; resonant wave-particle interactions; two-band chorus waves; Van Allen Probes |
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Generation of lower L -shell dayside chorus by energetic electrons from the plasmasheet Currently, the generation mechanism for the lower L-shell dayside chorus has still remained an open question. Here, we report two storm events: 06-07 March 2016 and 20-21 January 2016, when Van Allen Probes observed enhanced dayside chorus with lower and higher wave normal angles (the angles between the wave vector and the geomagnetic field) in the region of L = 3.5-6.3 and MLT = 5.6-13.5. Hot and energetic (\~ 1-100 keV) electrons displayed enhancements in fluxes and anisotropy when they were injected from the plasmasheet a ... He, Yihua; Xiao, Fuliang; Su, Zhenpeng; Zheng, Huinan; Yang, Chang; Liu, Si; Zhou, Qinghua; YEAR: 2018 DOI: 10.1029/2017JA024889 Dayside chorus generation; Radiation belt; Van Allen Probes; Wave-particle interaction |
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A Statistical Survey of Radiation Belt Dropouts Observed by Van Allen Probes A statistical analysis on the radiation belt dropouts is performed based on 4 years of electron phase space density data from the Van Allen Probes. The μ, K, and L* dependence of dropouts and their driving mechanisms and geomagnetic and solar wind conditions are investigated using electron phase space density data sets for the first time. Our results suggest that electronmagnetic ion cyclotron (EMIC) wave scattering is the dominant dropout mechanism at low L* region, which requires the most active geomagnetic and solar wind ... Xiang, Zheng; Tu, Weichao; Ni, Binbin; Henderson, M.; Cao, Xing; YEAR: 2018 DOI: 10.1029/2018GL078907 EMIC wave; magnetopause shadowing; Phase space density; radial diffusion; radiation belt dropout; Van Allen Probes; wave particle interaction |
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Observations of impulsive electric fields induced by Interplanetary Shock We investigate the characteristics of impulsive electric fields in Earth\textquoterights magnetosphere, as measured by the Van Allen Probes, in association with interplanetary shocks, as measured by ACE and Wind spacecraft in the solar wind from January 2013 to July 2016. It is shown that electric field impulses are mainly induced by global compressions by the shocks, mostly in the azimuthal direction and the amplitudes of the initial electric field impulses are positively correlated with the rate of increase of dynamic pres ... Zhang, Dianjun; Liu, Wenlong; Li, Xinlin; Sarris, Theodore; Xiao, Chao; Wygant, J.; YEAR: 2018 DOI: 10.1029/2018GL078809 electric field; inner magnetosphere; interplanetary shock; particle accelaration; Van Allen Probes |
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Observed propagation route of VLF transmitter signals in the magnetosphere Signals of powerful ground transmitters at various places have been detected by satellites in near-Earth space. The study on propagation mode, ducted or nonducted, has attracted much attentions for several decades. Based on the statistical results from Van Allen Probes (data from Oct. 2012 to Mar. 2017) and DEMETER satellite (from Jan. 2006 to Dec. 2007), we present the ground transmitter signals distributed clearly in ionosphere and magnetosphere. The observed propagation route in the meridian plane in the magnetosphere for ... Zhang, Zhenxia; Chen, Lunjin; Li, Xinqiao; Xia, Zhiyang; Heelis, Roderick; Horne, Richard; YEAR: 2018 DOI: 10.1029/2018JA025637 ducted propagation; in magnetosphere; nonducted propagation; Van Allen Probes; VLF transmitter |
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Electron Scattering by Plasmaspheric Hiss in a Nightside Plume Plasmaspheric hiss is known to play an important role in radiation belt electron dynamics in high plasma density regions. We present observations of two crossings of a plasmaspheric plume by the Van Allen Probes on 26 December 2012, which occurred unusually at the post-midnight-to-dawn sector between L ~ 4\textendash6 during a geomagnetically quiet period. This plume exhibited pronounced electron densities higher than those of the average plume level. Moderate hiss emissions accompanied the two plume crossings with the peak ... Zhang, Wenxun; Fu, Song; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Summers, Danny; Zou, Zhengyang; Cao, Xing; Lou, Yuequn; Hua, Man; YEAR: 2018 DOI: 10.1029/2018GL077212 Electron scattering; nightside plumes; Plasmaspheric Hiss; Van Allen Probes |
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Previous studies have revealed a typical picture that seed electrons are transported inward under the drive of radial diffusion and then accelerated via chorus to relativistic energies. Here we show a potentially different process during the 2\textendash3 October 2013 storm when Van Allen Probes observed extremely rapid (by about 50 times in 2 h) flux enhancements of relativistic (1.8\textendash3.4 MeV) electrons but without distinct chorus at lower L-shells. Meanwhile, Time History of Events and Macroscale Interactions duri ... Liu, Si; Yan, Qi; Yang, Chang; Zhou, Qinghua; He, Zhaoguo; He, Yihua; Gao, Zhonglei; Xiao, Fuliang; YEAR: 2018 DOI: 10.1002/grl.v45.310.1002/2017GL076513 chorus-driven acceleration; radial diffusion; Radiation belt; THEMIS; Van Allen Probes |
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Resonant Scattering of Radiation Belt Electrons by Off-Equatorial Magnetosonic Waves Fast magnetosonic (MS) waves are commonly regarded as electromagnetic waves that are characteristically confined within \textpm3\textdegree of the geomagnetic equator. We report two typical off-equatorial MS events observed by Van Allen Probes, that is, the 8 May 2014 event that occurred at the geomagnetic latitudes of 7.5\textdegree\textendash9.2\textdegree both inside and outside the plasmasphere with the wave amplitude up to 590 pT and the 9 January 2014 event that occurred at the latitudes of\textemdash(15.7\textdegree\t ... Ni, Binbin; Zou, Zhengyang; Fu, Song; Cao, Xing; Gu, Xudong; Xiang, Zheng; YEAR: 2018 DOI: 10.1002/grl.v45.310.1002/2017GL075788 butterfly pitch angle distributions; off-equatorial MS waves; radiation belt electrons; Van Allen Probes |
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During the 13-14 November 2012 storm, Van Allen Probe A simultaneously observed a 10-h period of enhanced chorus (including quasi-parallel and oblique propagation components) and relativistic electron fluxes over a broad range of L = 3-6 and MLT=2 - 10 within a complete orbit cycle. By adopting a Gaussian fit to the observed wave spectra, we obtain the wave parameters and calculate the bounce-averaged diffusion coefficients. We solve the Fokker-Planck diffusion equation to simulate flux evolutions of relativistic (1.8-4.2 Me ... Yang, Chang; Xiao, Fuliang; He, Yihua; Liu, Si; Zhou, Qinghua; Guo, Mingyue; Zhao, Wanli; YEAR: 2018 DOI: 10.1002/2017GL075894 energetic electron; Geomagnetic storm; outer radiation belt; Van Allen Probes; Wave-particle interaction; whistler-mode chorus wave |
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The effect of the plasmapause on equatorially radially propagating fast magnetosonic (MS) waves in the Earth\textquoterights 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 i ... Liu, Xu; Chen, Lunjin; Yang, Lixia; Xia, Zhiyang; Malaspina, David; YEAR: 2018 DOI: 10.1002/2017JA024336 fine-scale density structure; finite difference time domain; magnetosonic wave; Plasmapause; Van Allen Probes |
| 2017 |
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Multiple-satellite observation of magnetic dip event during the substorm on 10 October, 2013 We present a multiple-satellite observation of the magnetic dip event during the substorm on October 10, 2013. The observation illustrates the temporal and spatial evolution of the magnetic dip and gives a compelling evidence that ring current ions induce the magnetic dip by enhanced plasma beta. The dip moves with the energetic ions in a comparable drift velocity and affects the dynamics of relativistic electrons in the radiation belt. In addition, the magnetic dip provides a favorable condition for the EMIC wave generation ... He, Zhaoguo; Chen, Lunjin; Zhu, Hui; Xia, Zhiyang; Reeves, G.; Xiong, Ying; Xie, Lun; Cao, Yong; YEAR: 2017 DOI: 10.1002/2017GL074869 EMIC wave; magnetic dip; radiation belt electrons; Ring current ions; Van Allen Probes |
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Previous theoretical studies have shown that dayside chorus can produce butterfly distribution of energetic electrons in the Earth\textquoterights radiation belts by preferentially accelerating medium pitch angle electrons, but this requires the further confirmation from high-resolution satellite observation. Here, we report correlated Van Allen Probes data on wave and particle during the 11\textendash13 April, 2014 geomagnetic storm. We find that a butterfly pitch angle distribution of relativistic electrons is formed aroun ... Jin, YuYue; Yang, Chang; He, Yihua; Liu, Si; Zhou, Qinghua; Xiao, Fuliang; YEAR: 2017 DOI: 10.1007/s11431-017-9067-y butterfly distribution relativistic electrons radiation belts wave-particle interaction dayside chorus; Van Allen Probes |
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Understanding the Mechanisms of Radiation Belt Dropouts Observed by Van Allen Probes To achieve a better understanding of the dominant loss mechanisms for the rapid dropouts of radiation belt electrons, three distinct radiation belt dropout events observed by Van Allen Probes are comprehensively investigated. For each event, observations of the pitch angle distribution of electron fluxes and electromagnetic ion cyclotron (EMIC) waves are analyzed to determine the effects of atmospheric precipitation loss due to pitch angle scattering induced by EMIC waves. Last closed drift shells (LCDS) and magnetopause sta ... Xiang, Zheng; Tu, Weichao; Li, Xinlin; Ni, Binbin; Morley, S.; Baker, D.; YEAR: 2017 DOI: 10.1002/2017JA024487 EMIC wave; last closed drift shell; magnetopause shadowing; Phase space density; radiation belt dropout; Van Allen Probes |
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Electrostatic electron cyclotron harmonic (ECH) waves generated by the electron loss cone distribution can produce efficient scattering loss of plasma sheet electrons, which has a significant effect on the dynamics in the outer magnetosphere. Here we report two ECH emission events around the same location L≈ 5.7\textendash5.8, MLT ≈ 12 from Van Allen Probes on 11 February (event A) and 9 January 2014 (event B), respectively. The spectrum of ECH waves was centered at the lower half of the harmonic bands during event A, bu ... Zhou, Qinghua; Xiao, Fuliang; Yang, Chang; Liu, Si; He, Yihua; Baker, D.; Spence, H.; Reeves, G.; Funsten, H.; YEAR: 2017 DOI: 10.1002/2017GL073051 ECH waves; RBSP results; Van Allen Probes; Wave-particle interaction |
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Dayside modulated relativistic electron\textquoterights butterfly pitch angle distributions (PADs) from \~200 keV to 2.6 MeV were observed by Van Allen Probe B at L = 5.3 on 15 November 2013. They were associated with localized magnetic dip driven by hot ring current ion (60\textendash100 keV proton and 60\textendash200 keV helium and oxygen) injections. We reproduce the electron\textquoterights butterfly PADs at satellite\textquoterights location using test particle simulation. The simulation results illustrate that a negat ... Xiong, Ying; Chen, Lunjin; Xie, Lun; Fu, Suiyan; Xia, Zhiyang; Pu, Zuyin; YEAR: 2017 DOI: 10.1002/2017GL072558 butterfly distribution; Radiation belt; ring current; Van Allen Probes |
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Variations of the relativistic electron flux after a magnetospheric compression event On January 21, 2015, a sharp increase of the solar wind dynamic pressure impacted the magnetosphere. The magnetopause moved inward to the region L< 8 without causing a geomagnetic storm. The flux of the relativistic electrons in the outer radiation belt decreased by half during this event based on the observations of the particle radiation monitor (PRM) of the fourth of the China-Brazil Earth Resource Satellites (CBERS-4). The flux remained low for approximately 11 d; it did not recover after a small magnetic storm on Januar ... Chen, Zhe; Chen, HongFei; Li, YiFan; Xiang, HongWen; Yu, XiangQian; Shi, WeiHong; Hao, ZhiHua; Zou, Hong; Zou, JiQing; Zhong, WeiYing; YEAR: 2017 DOI: 10.1007/s11431-016-9008-3 outer radiation belt high-energy electrons medium-energy electrons space environment; Van Allen Probes |
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Generation of extremely low frequency chorus in Van Allen radiation belts Recent studies have shown that chorus can efficiently accelerate the outer radiation belt electrons to relativistic energies. Chorus, previously often observed above 0.1 equatorial electron gyrofrequency fce, was generated by energetic electrons originating from Earth\textquoterights plasma sheet. Chorus below 0.1 fce has seldom been reported until the recent data from Van Allen Probes, but its origin has not been revealed so far. Because electron resonant energy can approach the relativistic level at extremely low frequency ... Xiao, Fuliang; Liu, Si; Tao, Xin; Su, Zhenpeng; Zhou, Qinghua; Yang, Chang; He, Zhaoguo; He, Yihua; Gao, Zhonglei; Baker, D.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.; YEAR: 2017 DOI: 10.1002/2016JA023561 ELF chorus waves; RBSP results; relativistic distribution; Van Allen Probes; Wave-particle interaction |
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Zhang, Yang; Shi, Run; Ni, Binbin; Gu, Xudong; Zhang, Xianguo; Zuo, Pingbing; Fu, Song; Xiang, Zheng; Wang, Qi; Cao, Xing; Zou, Zhengyang; YEAR: 2017 DOI: 10.1016/j.asr.2016.12.035 |
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Energetic (hundreds of keV) electrons in the radiation belt slot region have been found to exhibit the butterfly pitch angle distributions. Resonant interactions with magnetosonic and whistler-mode waves are two potential mechanisms for the formation of these peculiar distributions. Here we perform a statistical study of energetic electron pitch angle distribution characteristics measured by Van Allen Probes in the slot region during a three-year period from May 2013 to May 2016. Our results show that electron butterfly dist ... Yang, Chang; Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; Wang, Shui; Spence, H.; Reeves, G.; Baker, D.; Blake, J.; Funsten, H.; YEAR: 2017 DOI: 10.1002/2017GL073116 butterfly distributions; Electron acceleration; Landau resonance; magnetosonic wave; Radiation belt; Van Allen Probes; Wave-particle interaction |
| 2016 |
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Explaining occurrences of auroral kilometric radiation in Van Allen radiation belts Auroral kilometric radiation (AKR) is a strong terrestrial radio emission and dominates at higher latitudes because of reflection in vicinities of the source cavity and plasmapause. Recently, Van Allen Probes have observed occurrences of AKR emission in the equatorial region of Earth\textquoterights radiation belts but its origin still remains an open question. Equatorial AKR can produce efficient acceleration of radiation belt electrons and is a risk to space weather. Here we report high-resolution observations during two s ... Xiao, Fuliang; Zhou, Qinghua; Su, Zhenpeng; He, Zhaoguo; Yang, Chang; Liu, Si; He, Yihua; Gao, Zhonglei; YEAR: 2016 DOI: 10.1002/2016GL071728 AKR emissions; Geomagnetic storms; Radiation belts; ray tracing simulations; satellite data; Van Allen Probes |
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Modulation of chorus intensity by ULF waves deep in the inner magnetosphere Previous studies have shown that chorus wave intensity can be modulated by Pc4-Pc5 compressional ULF waves. In this study, we present Van Allen Probes observation of ULF wave modulating chorus wave intensity, which occurred deep in the magnetosphere. The ULF wave shows fundamental poloidal mode signature and mirror mode compressional nature. The observed ULF wave can modulate not only the chorus wave intensity but also the distribution of both protons and electrons. Linear growth rate analysis shows consistence with observed ... Xia, Zhiyang; Chen, Lunjin; Dai, Lei; Claudepierre, Seth; Chan, Anthony; Soto-Chavez, A.; Reeves, G.; YEAR: 2016 DOI: 10.1002/2016GL070280 chorus modulation; inner magnetosphere; ULF wave; Van Allen Probes; whistler wave |
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Multiband electromagnetic ion cyclotron (EMIC) waves can drive efficient scattering loss of radiation belt relativistic electrons. However, it is statistically uncommon to capture the three bands of EMIC waves concurrently. Utilizing data from the Electric and Magnetic Field Instrument Suite and Integrated Science magnetometer onboard Van Allen Probe A, we report the simultaneous presence of three (H+, He+, and O+) emission bands in an EMIC wave event, which provides an opportunity to look into the combined scattering effect ... He, Fengming; Cao, Xing; Ni, Binbin; Xiang, Zheng; Zhou, Chen; Gu, Xudong; Zhao, Zhengyu; Shi, Run; Wang, Qi; YEAR: 2016 DOI: 10.1002/2016JA022483 combined scattering rates; electromagnetic ion cyclotron waves; loss timescales; radiation belt relativistic electrons; resonant wave-particle interactions; Van Allen Probes |
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Evolution of chorus emissions into plasmaspheric hiss observed by Van Allen Probes The two classes of whistler mode waves (chorus and hiss) play different roles in the dynamics of radiation belt energetic electrons. Chorus can efficiently accelerate energetic electrons, and hiss is responsible for the loss of energetic electrons. Previous studies have proposed that chorus is the source of plasmaspheric hiss, but this still requires an observational confirmation because the previously observed chorus and hiss emissions were not in the same frequency range in the same time. Here we report simultaneous observ ... Zhou, Qinghua; Xiao, Fuliang; Yang, Chang; Liu, Si; He, Yihua; Wygant, J.; Baker, D.; Spence, H.; Reeves, G.; Funsten, H.; YEAR: 2016 DOI: 10.1002/2016JA022366 chorus waves; Plasmaspheric Hiss; RBSP results; Van Allen Probes |
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Frequency distribution is a vital factor in determining the contribution of whistler-mode chorus to radiation belt electron dynamics. Chorus is usually considered to occur in the frequency range 0.1\textendash0.8 inline image (with the equatorial electron gyrofrequency inline image). We here report an event of intense low-frequency chorus with nearly half of wave power distributed below 0.1 inline image observed by Van Allen Probe A on 27 August 2014. This emission propagated quasi-parallel to the magnetic field and exhibi ... Gao, Zhonglei; Su, Zhenpeng; Zhu, Hui; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; Shen, Chao; Wang, Shui; YEAR: 2016 DOI: 10.1002/2016GL067687 Cyclotron resonance; Hiss-like band; Low-frequency chorus; Radiation belt; Van Allen Probes; Rising tones; Van Allen Probes |
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Ultra-low-frequency wave-driven diffusion of radiation belt relativistic electrons Van Allen radiation belts are typically two zones of energetic particles encircling the Earth separated by the slot region. How the outer radiation belt electrons are accelerated to relativistic energies remains an unanswered question. Recent studies have presented compelling evidence for the local acceleration by very-low-frequency (VLF) chorus waves. However, there has been a competing theory to the local acceleration, radial diffusion by ultra-low-frequency (ULF) waves, whose importance has not yet been determined definit ... Su, Zhenpeng; Zhu, Hui; Xiao, Fuliang; Zong, Q.-G.; Zhou, X.-Z.; Zheng, Huinan; Wang, Yuming; Wang, Shui; Hao, Y.-X.; Gao, Zhonglei; He, Zhaoguo; Baker, D.; Spence, H.; Reeves, G.; Blake, J.; Wygant, J.; YEAR: 2015 DOI: 10.1038/ncomms10096 |
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Penetration of magnetosonic waves into the plasmasphere observed by the Van Allen Probes During the small storm on 14\textendash15 April 2014, Van Allen Probe A measured a continuously distinct proton ring distribution and enhanced magnetosonic (MS) waves along its orbit outside the plasmapause. Inside the plasmasphere, strong MS waves were still present but the distinct proton ring distribution was falling steeply with distance. We adopt a sum of subtracted bi-Maxwellian components to model the observed proton ring distribution and simulate the wave trajectory and growth. MS waves at first propagate toward lowe ... Xiao, Fuliang; Zhou, Qinghua; He, Yihua; Yang, Chang; Liu, Si; Baker, D.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.; YEAR: 2015 DOI: 10.1002/2015GL065745 Geomagnetic storms; magnetosonic waves; proton ring distribution; Radiation belts; Van Allen Probe results; Van Allen Probes; Wave-particle interaction |
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We report correlated data on nightside chorus waves and energetic electrons during two small storm periods: 1 November 2012 (Dst≈-45) and 14 January 2013 (Dst≈-18). The Van Allen Probes simultaneously observed strong chorus waves at locations L = 5.8 - 6.3, with a lower frequency band 0.1 - 0.5fce and a peak spectral density \~[10-4 nT2/Hz. In the same period, the fluxes and anisotropy of energetic (\~ 10-300 keV) electrons were greatly enhanced in the interval of large negative interplanetary magnetic field Bz. Using a ... He, Yihua; Xiao, Fuliang; Zhou, Qinghua; Yang, Chang; Liu, Si; Baker, D.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.; YEAR: 2015 DOI: 10.1002/2015JA021376 chorus wave excitation; energetic electrons; Geomagnetic storm; Van Allen Probes; Van Allen probes results; Wave-particle interaction |
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Wave-driven butterfly distribution of Van Allen belt relativistic electrons Van Allen radiation belts consist of relativistic electrons trapped by Earth\textquoterights magnetic field. Trapped electrons often drift azimuthally around Earth and display a butterfly pitch angle distribution of a minimum at 90\textdegree further out than geostationary orbit. This is usually attributed to drift shell splitting resulting from day\textendashnight asymmetry in Earth\textquoterights magnetic field. However, direct observation of a butterfly distribution well inside of geostationary orbit and the origin of th ... Xiao, Fuliang; Yang, Chang; Su, Zhenpeng; Zhou, Qinghua; He, Zhaoguo; He, Yihua; Baker, D.; Spence, H.; Funsten, H.; Blake, J.; YEAR: 2015 DOI: 10.1038/ncomms9590 |
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Disappearance of plasmaspheric hiss following interplanetary shock Plasmaspheric hiss is one of the important plasma waves controlling radiation belt dynamics. Its spatiotemporal distribution and generation mechanism are presently the object of active research. We here give the first report on the shock-induced disappearance of plasmaspheric hiss observed by the Van Allen Probes on 8 October 2013. This special event exhibits the dramatic variability of plasmaspheric hiss and provides a good opportunity to test its generation mechanisms. The origination of plasmaspheric hiss from plasmatroug ... Su, Zhenpeng; Zhu, Hui; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; Shen, Chao; Zhang, Min; Wang, Shui; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.; Baker, D.; Wygant, J.; YEAR: 2015 DOI: 10.1002/2015GL063906 Cyclotron instability; Cyclotron resonance; interplanetary shock; Landau damping; Plasmaspheric Hiss; Radiation belt; Van Allen Probes |
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Exohiss waves are whistler mode hiss observed in the plasmatrough region. We present a case study of exohiss waves and the corresponding background plasma distributions observed by the Van Allen Probes in the dayside low-latitude region. The analysis of wave Poynting fluxes, suprathermal electron fluxes and cold electron densities supports the scenario that exohiss leaks from the plasmasphere into the plasmatrough. Quasilinear calculations further reveal that exohiss can potentially cause the resonant scattering loss of radi ... Zhu, Hui; Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; Shen, Chao; Xian, Tao; Wang, Shui; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Funsten, H.; Blake, J.; Baker, D.; YEAR: 2015 DOI: 10.1002/2014GL062964 Cyclotron resonance; Exohiss; Landau damping; Plasmaspheric Hiss; Radiation belt electron loss; Van Allen Probes |
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