Bibliography



Found 88 entries in the Bibliography.


Showing entries from 1 through 50


2021

Realistic electron diffusion rates and lifetimes due to scattering by electron holes

AbstractPlasma sheet electron precipitation into the diffuse aurora is critical for magnetosphere-ionosphere coupling. Recent studies have shown that electron phase space holes can pitch-angle scatter electrons and may produce plasma sheet electron precipitation. These studies have assumed identical electron hole parameters to estimate electron scattering rates (Vasko et al., 2018). In this study, we have re-evaluated the efficiency of this scattering by incorporating realistic electron hole properties from direct spacecraf ...

Shen, Yangyang; Vasko, Ivan; Artemyev, Anton; Malaspina, David; Chu, Xiangning; Angelopoulos, Vassilis; Zhang, Xiao-Jia;

YEAR: 2021     DOI: https://doi.org/10.1029/2021JA029380

diffuse aurora; electron pitch-angle scattering; electron phase space hole; Wave-particle interaction; electron lifetimes; broadband electrostatic fluctuations; Van Allen Probes

Trapping and amplification of unguided mode EMIC waves in the radiation belt

AbstractElectromagnetic ion cyclotron (EMIC) waves can cause the scattering loss of the relativistic electrons in the radiation belt. They can be classified into the guided mode and the unguided mode, according to waves propagation behavior. The guided mode waves have been widely investigated in the radiation belt, but the observation of the unguided mode waves have not been expected. Based on the observations of Van Allen Probes, we demonstrate for the first time the existence of the intense unguided L-mode EMIC waves in th ...

Wang, Geng; Gao, Zhonglei; Wu, MingYu; Wang, GuoQiang; Xiao, SuDong; Chen, YuanQiang; Zou, Zhengyang; Zhang, TieLong;

YEAR: 2021     DOI: https://doi.org/10.1029/2021JA029322

EMIC waves; unguided mode; Radiation belt; ion abundance ratios; Wave trapping; growth rate; Van Allen Probes

Global Survey of Electron Precipitation due to Hiss Waves in the Earth s Plasmasphere and Plumes

Abstract We present a global survey of energetic electron precipitation from the equatorial magnetosphere due to hiss waves in the plasmasphere and plumes. Using Van Allen Probes measurements, we calculate the pitch angle diffusion coefficients at the bounce loss cone, and evaluate the energy spectrum of precipitating electron flux. Our ∼6.5-year survey shows that, during disturbed times, hiss inside the plasmasphere primarily causes the electron precipitation at L > 4 over 8 h < MLT < 18 h, and hiss waves in plumes cause ...

Ma, Q.; Li, W.; Zhang, X.-J.; Bortnik, J.; Shen, X.-C.; Connor, H.; Boyd, A.; Kurth, W.; Hospodarsky, G.; Claudepierre, S.; Reeves, G.; Spence, H.;

YEAR: 2021     DOI: https://doi.org/10.1029/2021JA029644

electron precipitation; hiss wave; plasmasphere; plasmaspheric plume; Precipitating Energy Flux; Van Allen Probes Survey; Van Allen Probes

Van Allen Probes Observations of Multi-MeV Electron Drift-Periodic Flux Oscillations in Earth’s Outer Radiation Belt During the March 2017 Event

Abstract Radiation belt electrons undergo frequent acceleration, transport, and loss processes under various physical mechanisms. One of the most prevalent mechanisms is radial diffusion, caused by the resonant interactions between energetic electrons and ULF waves in the Pc4-5 band. An indication of this resonant interaction is believed to be the appearance of periodic flux oscillations. In this study, we report long-lasting, drift-periodic flux oscillations of relativistic and ultrarelativistic electrons with energies up t ...

Zhao, Hong; Sarris, Theodore; Li, Xinlin; Weiner, Max; Huckabee, Isabela; Baker, Daniel; Jaynes, Allison; Kanekal, Shrikanth; Elkington, Scot; Barani, Mohammad; Tu, Weichao; Liu, Wenlong; Zhang, Dianjun; Hartinger, Michael;

YEAR: 2021     DOI: https://doi.org/10.1029/2021JA029284

Radiation belt; multi-MeV electrons; radial diffusion; ULF waves; Wave-particle interaction; Phase space density radial gradient; Van Allen Probes

Statistics of Magnetosonic Waves in the Slot Region Observed by Van Allen Probes

Abstract We perform a statistical analysis of magnetosonic waves in the slot region based on Van Allen Probes observations from September 2012 to February 2018. Our results demonstrate that the wave occurrence rate increases with enhanced geomagnetic activity and decreasing magnetic latitude, with the presence of strongest slot region magnetosonic waves near the geomagnetic equator within the 08-20 MLT sector. Power spectral densities of slot region magnetosonic waves also intensify during geomagnetically active times, with ...

Yan, Ling; Cao, Xing; Hua, Man; Ni, Binbin; Zhang, Yuannong;

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL094015

magnetosonic waves; Slot region; Statistical distribution; Van Allen Probes

The Link between Wedge-like and Nose-like Ion Spectral Structures in the Inner Magnetosphere

AbstractThe wedge-like and nose-like ion spectral structures, named after their characteristic shapes in the energy-time spectrograms, appear to be distinctively different structures in the Earth s inner magnetosphere. Here we present a case study with conjugate observations from the Arase spacecraft and the twin Van Allen Probes on July 1 and 2, 2017, which displayed the characteristic signatures of the wedge-like and nose-like ion structures, respectively. When the spacecraft nearly intersected at L =2.8, the two structure ...

Ren, Jie; Zhou, Xu-Zhi; Zong, Qiu-Gang; Yue, Chao; Fu, Sui-Yan; Miyoshi, Y.; Zhang, Xiao-Xin; Asamura, K.; Shinohara, I.;

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL093930

Van Allen Probes

Observation of unusual chorus elements by Van Allen Probes

AbstractWhistler mode chorus waves play an important role in the radiation belt dynamics, which usually appear as discrete elements with frequency sweeping. Finer structure analysis shows that a chorus element is composed of several frequency-sweeping subelements, and such two-level structures can be successfully reproduced by modeling based on nonlinear theories. Previous observations and models suggest that an element and its subelements should have the same frequency-sweep direction. However, we here present two unexpecte ...

Liu, Si; Gao, Zhonglei; Xiao, Fuliang; He, Qian; Li, Tong; Shang, Xiongjun; Zhou, Qinghua; Yang, Chang; Zhang, Sai;

YEAR: 2021     DOI: https://doi.org/10.1029/2021JA029258

Van Allen Probes

Modeling the Dynamics of Radiation Belt Electrons with Source and Loss Driven by the Solar Wind

Abstract A radial diffusion model directly driven by the solar wind is developed to reproduce MeV electron variations between L=2-12 (L is L* in this study) from October 2012 to April 2015. The radial diffusion coefficient, internal source rate, quick loss due to EMIC waves, and slow loss due to hiss waves are all expressed in terms of the solar wind speed, dynamic pressure, and interplanetary magnetic field (IMF). The model achieves a prediction efficiency (PE) of 0.45 at L=5 and 0.51 at L=4 after converting the electron ph ...

Xiang, Zheng; Li, Xinlin; Kapali, Sudha; Gannon, Jennifer; Ni, Binbin; Zhao, Hong; Zhang, Kun; Khoo, Leng;

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028988

Radiation belt; Solar wind; flux prediction; radial diffusion; magnetopause shadowing; wave-particle interactions; Van Allen Probes

A Concise Empirical Formula for the Field-aligned Distribution of Auroral Kilometeric Radiation based on Arase satellite and Van Allen Probes

Abstract Auroral kilometric radiations (AKR) are strong radio emission phenomena, and can prduce significant acceleration or scattering of radiation belt electrons. The variation of AKR wave amplitude with the latitude (λ) has not been reported so far owing to lack of measurements. Here, using observations of the Arase satellite and Van Allen Probes from 23 March 2017 to 31 July 2019, we present the first statistical study on the AKR electric field amplitude (Et) in the radiation belts for |λ| = 0° − 40° and L-shell L ...

Zhang, Sai; Liu, Si; Li, Wentao; He, Yihua; Yang, Qiwu; Xiao, Fuliang; Kumamoto, Atsushi; Miyoshi, Yoshizumi; Nakamura, Yosuke; Tsuchiya, Fuminori; Kasahara, Yoshiya; Shinohara, Iku;

YEAR: 2021     DOI: https://doi.org/10.1029/2021GL092805

AKR; wave amplitude; geomagnetic latitude; Radiation belt; field-aligned; Van Allen Probes

Empirical loss timescales of slot region electrons due to plasmaspheric hiss based on Van Allen Probes observations

Abstract Based on Van Allen Probes observations, in this study we perform a statistical analysis of the spectral intensities of plasmaspheric hiss at L-shells of 1.8 – 3.0 in the slot region. Our results show that slot region hiss power intensifies with a strong day-night asymmetry as the level of substorm activity or L-shell increases. Using the statistical spectral profiles of plasmaspheric hiss, we calculate the drift- and bounce-averaged electron pitch angle diffusion coefficients and subsequently obtain the resultant ...

Zhu, Qi; Cao, Xing; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Fu, Song; Summers, Danny; Hua, Man; Lou, Yuequn; Ma, Xin; Guo, YingJie; Guo, DeYu; Zhang, Wenxun;

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029057

Plasmaspheric Hiss; Slot region; Electron loss timescales; Van Allen Probes

Dependence of Relativistic Electron Precipitation in the Ionosphere on EMIC Wave Minimum Resonant Energy at the Conjugate Equator

Abstract We investigate relativistic electron precipitation events detected by POES in low-Earth orbit in close conjunction with Van Allen Probe A observations of EMIC waves near the geomagnetic equator. We show that the occurrence rate of > 0.7 MeV electron precipitation recorded by POES during those times strongly increases, reaching statistically significant levels when the minimum electron energy for cyclotron resonance with hydrogen or helium band EMIC waves at the equator decreases below ≃ 1.0 − 2.5 MeV, as expecte ...

Zhang, X.-J.; Mourenas, D.; Shen, X.-C.; Qin, M.; Artemyev, A.; Ma, Q.; Li, W.; Hudson, M.; Angelopoulos, V.;

YEAR: 2021     DOI: https://doi.org/10.1029/2021JA029193

EMIC waves; relativistic electron precipitation; minimum resonant energy; Van Allen Probes; POES; Radiation belts

Pitch Angle Phase Shift in Ring Current Ions Interacting with ULF Waves: Van Allen Probes Observations

Abstract Drift-bounce resonance between ultra-low-frequency (ULF) waves and ring current ions has been widely studied, because of its important role in ring current acceleration and relevant geomagnetic activities. To identify drift-bounce resonance in observations, 180° phase shifts across resonant pitch angle have been proposed as diagnostic signatures. This study, however, presents observations that suggest this criterion may be invalid when phase space density (PSD) distributions vary non-monochromatically with energy. ...

Li, Xing-Yu; Liu, Zhi-Yang; Zong, Qiu-Gang; Zhou, Xu-Zhi; Hao, Yi-Xin; Rankin, Robert; Zhang, Xiao-Xin;

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA029025

ring current; ultra-low-frequency waves; drift-bounce resonance; Van Allen Probes

Generation of realistic short chorus wave packets

Abstract Most lower-band chorus waves observed in the inner magnetosphere propagate under the form of moderately intense short wave packets with fast frequency and phase variations. Therefore, understanding the formation mechanism of such short wave packets is crucial for accurately modelling electron nonlinear acceleration or precipitation into the atmosphere by these waves. We compare chorus wave statistics from the Van Allen Probes with predictions from a simple model of short wave packet generation by wave superposition ...

Nunn, D.; Zhang, X.-J.; Mourenas, D.; Artemyev, A.;

YEAR: 2021     DOI: https://doi.org/10.1029/2020GL092178

chorus waves; Radiation belts; Wave-particle interaction; Van Allen Probes

Determining the Temporal and Spatial Coherence of Plasmaspheric Hiss Waves in the Magnetosphere

Abstract Plasmaspheric hiss is one of the most important plasma waves in the Earth s magnetosphere to contribute to radiation belt dynamics by pitch-angle scattering energetic electrons via wave-particle interactions. There is growing evidence that the temporal and spatial variability of wave-particle interactions are important factors in the construction of diffusion-based models of the radiation belts. Hiss amplitudes are thought to be coherent across large distances and on long timescales inside the plasmapause, which mea ...

Zhang, Shuai; Rae, Jonathan; Watt, Clare; Degeling, Alexander; Tian, Anmin; Shi, Quanqi; Shen, Xiao-Chen; Smith, Andy; Wang, Mengmeng;

YEAR: 2021     DOI: https://doi.org/10.1029/2020JA028635

Van Allen Probes

2020

Global Propagation of Magnetospheric Pc5 ULF Waves Driven by Foreshock Transients

Pc5 (2–7 mHz) ultralow frequency (ULF) waves play a significant role in resonating with particles and transferring energy in the coupled magnetospheric and ionospheric system. Recent studies found that Pc5 ULF waves can be triggered by foreshock transients which can perturb the magnetopause through dynamic pressure variation. However, whether foreshock transient-driven Pc5 ULF waves are geoeffective and can propagate globally is still poorly understood. In this study, we take advantage of the conjunction between in situ (b ...

Wang, Boyi; Liu, Terry; Nishimura, Yukitoshi; Zhang, Hui; Hartinger, Michael; Shi, Xueling; Ma, Qianli; Angelopoulos, Vassilis; Frey, Harald;

YEAR: 2020     DOI: https://doi.org/10.1029/2020JA028411

ULF wave; Field line resonance; wave number; global; THEMIS; aurora; Van Allen Probes

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

Van Allen Probes

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

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

Long-Term Dropout of Relativistic Electrons in the Outer Radiation Belt During Two Sequential Geomagnetic Storms

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

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

New Insights From Long-Term Measurements of Inner Belt Protons (10s of MeV) by SAMPEX, POES, Van Allen Probes, and Simulation Results

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

Dynamics of Energetic Electrons in the Slot Region During Geomagnetically Quiet Times: Losses Due to Wave-Particle Interactions Versus a Source From Cosmic Ray Albedo Neutron Decay (CRAND)

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

Global Survey of Plasma Sheet Electron Precipitation due to Whistler Mode Chorus Waves in Earth s Magnetosphere

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

An empirical model of the global distribution of plasmaspheric hiss based on Van Allen Probes EMFISIS measurements

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

hiss; Van Allen Probes; global model

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

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

Decay of Ultrarelativistic Remnant Belt Electrons Through Scattering by Plasmaspheric Hiss

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 ...

Pinto, V.; Mourenas, D.; Bortnik, J.; Zhang, X.-J.; Artemyev, A.; Moya, P.; Lyons, L.;

YEAR: 2019     DOI: 10.1029/2019JA026509

Decay rates; EMIC waves; MeV Electron Decay; Plasmaspheric Hiss; Radiation belts; Remnant Belt; Van Allen Probes

How Sudden, Intense Energetic Electron Enhancements Correlate With the Innermost Plasmapause Locations Under Various Solar Wind Drivers and Geomagnetic Conditions

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

Propagation of EMIC Waves Inside the Plasmasphere: A Two-Event Study

Electromagnetic ion cyclotron (EMIC) waves are important for the loss of high-energy electrons in the radiation belt. Based on the measurements of Van Allen Probes, two events during the same storm period are presented to study the propagation of EMIC waves. In the first event, left-handed polarized EMIC waves were observed near the plasmapause, while right-handed waves were observed in the inner plasmasphere. The Poynting flux of the right-hand waves was mainly directed inward and equatorward, and no positive growth rates w ...

Wang, G.; Zhang, T.; Gao, Z.; . Y. Wu, M; Wang, G.; Schmid, D.;

YEAR: 2019     DOI: 10.1029/2019JA027055

density gradient; EMIC wave; inward propagation; refraction; right hand polarization; Snell\textquoterights law; Van Allen Probes

Global Occurrences of Auroral Kilometric Radiation Related to Suprathermal Electrons in Radiation Belts

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

The Evolution of a Pitch-Angle \textquotedblleftBite-Out\textquotedblright Scattering Signature Caused by EMIC Wave Activity: A Case Study

Electromagnetic ion cyclotron (EMIC) waves are understood to be one of the dominant drivers of relativistic electron loss from Earth\textquoterights radiation belts. Theory predicts that the associated gyroresonant wave-particle interaction results in a distinct energy-dependent \textquotedblleftbite-out\textquotedblright signature in the normalized flux distribution of electrons as they are scattered into the loss cone. We identify such signatures along with the responsible EMIC waves captured in situ by the Van Allen Probe ...

Bingley, L.; Angelopoulos, V.; Sibeck, D.; Zhang, X.; Halford, A.;

YEAR: 2019     DOI: 10.1029/2018JA026292

Van Allen Probes

Nonlinear Electron Interaction With Intense Chorus Waves: Statistics of Occurrence Rates

A comprehensive statistical analysis on 8 years of lower-band chorus wave packets measured by the Van Allen Probes and THEMIS spacecraft is performed to examine whether, when, and where these waves are above the theoretical threshold for nonlinear resonant wave-particle interaction. We find that \~5\textendash30\% of all chorus waves interact nonlinearly with \~30- to 300-keV electrons possessing equatorial pitch angles of >40\textdegree in the outer radiation belt, especially during disturbed (AE>500 nT) periods with energe ...

Zhang, X.-J.; Mourenas, D.; Artemyev, A.; Angelopoulos, V.; Bortnik, J.; Thorne, R.; Kurth, W.; Kletzing, C.; Hospodarsky, G.;

YEAR: 2019     DOI: 10.1029/2019GL083833

chorus waves; Electron acceleration; nonlinear wave particle interaction; THEMIS; Van Allen Probes; wave packet size

Statistical Properties of Hiss in Plasmaspheric Plumes and Associated Scattering Losses of Radiation Belt Electrons

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

Energetic Electron Precipitation: Multievent Analysis of Its Spatial Extent During EMIC Wave Activity

Electromagnetic ion cyclotron (EMIC) waves can drive precipitation of tens of keV protons and relativistic electrons, and are a potential candidate for causing radiation belt flux dropouts. In this study, we quantitatively analyze three cases of EMIC-driven precipitation, which occurred near the dusk sector observed by multiple Low-Earth-Orbiting (LEO) Polar Operational Environmental Satellites/Meteorological Operational satellite programme (POES/MetOp) satellites. During EMIC wave activity, the proton precipitation occurred ...

Capannolo, L.; Li, W.; Ma, Q.; Shen, X.-C.; Zhang, X.-J.; Redmon, R.; Rodriguez, J.; Engebretson, M.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Spence, H.; Reeves, G.; Raita, T.;

YEAR: 2019     DOI: 10.1029/2018JA026291

EMIC waves; energetic electron precipitation; pitch angle scattering; quasi-linear theory; radiation belts dropouts; Van Allen Probes

Sensitivity of EMIC Wave-Driven Scattering Loss of Ring Current Protons to Wave Normal Angle Distribution

Electromagnetic ion cyclotron waves have long been recognized to play a crucial role in the dynamic loss of ring current protons. While the field-aligned propagation approximation of electromagnetic ion cyclotron waves was widely used to quantify the scattering loss of ring current protons, in this study, we find that the wave normal distribution strongly affects the pitch angle scattering efficiency of protons. Increase of peak normal angle or angular width can considerably reduce the scattering rates of <=10 keV protons. F ...

Cao, Xing; Ni, Binbin; Summers, Danny; Shprits, Yuri; Gu, Xudong; Fu, Song; Lou, Yuequn; Zhang, Yang; Ma, Xin; Zhang, Wenxun; Huang, He; Yi, Juan;

YEAR: 2019     DOI: 10.1029/2018GL081550

EMIC waves; Quasi-linear diffusion; Ring current protons; Van Allen Probes; wave-particle interactions

Sensitivity of EMIC Wave-Driven Scattering Loss of Ring Current Protons to Wave Normal Angle Distribution

Electromagnetic ion cyclotron waves have long been recognized to play a crucial role in the dynamic loss of ring current protons. While the field-aligned propagation approximation of electromagnetic ion cyclotron waves was widely used to quantify the scattering loss of ring current protons, in this study, we find that the wave normal distribution strongly affects the pitch angle scattering efficiency of protons. Increase of peak normal angle or angular width can considerably reduce the scattering rates of <=10 keV protons. F ...

Cao, Xing; Ni, Binbin; Summers, Danny; Shprits, Yuri; Gu, Xudong; Fu, Song; Lou, Yuequn; Zhang, Yang; Ma, Xin; Zhang, Wenxun; Huang, He; Yi, Juan;

YEAR: 2019     DOI: 10.1029/2018GL081550

EMIC waves; Quasi-linear diffusion; Ring current protons; Van Allen Probes; wave-particle interactions

2018

On the Initial Enhancement of Energetic Electrons and the Innermost Plasmapause Locations: CME-Driven Storm Periods

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

Combined Scattering of Outer Radiation Belt Electrons by Simultaneously Occurring Chorus, Exohiss, and Magnetosonic Waves

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

Combined Scattering of Outer Radiation Belt Electrons by Simultaneously Occurring Chorus, Exohiss, and Magnetosonic Waves

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

Evolution of electron distribution driven by nonlinear resonances with intense field-aligned chorus waves

Resonant electron interaction with whistler-mode chorus waves is recognized as one of the main drivers of radiation belt dynamics. For moderate wave intensity, this interaction is well described by quasi-linear theory. However, recent statistics of parallel propagating chorus waves have demonstrated that 5 - 20\% of the observed waves are sufficiently intense to interact nonlinearly with electrons. Such interactions include phase trapping and phase bunching (nonlinear scattering) effects not described by quasi-linear diffusi ...

Vainchtein, D.; Zhang, X.-J.; Artemyev, A.; Mourenas, D.; Angelopoulos, V.; Thorne, R.;

YEAR: 2018     DOI: 10.1029/2018JA025654

Van Allen Probes

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

Understanding the Driver of Energetic Electron Precipitation Using Coordinated Multisatellite Measurements

Magnetospheric plasma waves play a significant role in ring current and radiation belt dynamics, leading to pitch angle scattering loss and/or stochastic acceleration of the particles. During a non-storm time dropout event on 24 September 2013, intense electromagnetic ion cyclotron (EMIC) waves were detected by Van Allen Probe A (Radiation Belt Storm Probes-A). We quantitatively analyze a conjunction event when Van Allen Probe A was located approximately along the same magnetic field line as MetOp-01, which detected simultan ...

Capannolo, L.; Li, W.; Ma, Q.; Zhang, X.-J.; Redmon, R.; Rodriguez, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.; Engebretson, M.; Spence, H.; Reeves, G.;

YEAR: 2018     DOI: 10.1029/2018GL078604

EMIC waves; energetic particle precipitation; pitch angle scattering; Radiation belts; Van Allen Probes; wave particle interactions

Electron flux enhancements at L = 4.2 observed by Global Positioning System satellites: Relationship with solar wind and geomagnetic activity

Determining solar wind and geomagnetic activity parameters most favorable to strong electron flux enhancements is an important step towards forecasting radiation belt dynamics. Using electron flux measurements from Global Positioning System satellites at L = 4.2 in 2009-2016, we seek statistical relationships between flux enhancements at different energies and solar wind dynamic pressure Pdyn, AE, and Kp, from hundreds of events inside and outside the plasmasphere. Most ⩾1 MeV electron flux enhancements occur during non-st ...

Zhang, X.-J.; Mourenas, D.; Artemyev, A.; Angelopoulos, V.; Thorne, R.;

YEAR: 2018     DOI: 10.1029/2018JA025497

chorus waves; Electron energization; Electron flux enhancements; GPS satellites; Radiation belt; Solar wind and geomagnetic activities; Van Allen Probes

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

Plasma anisotropies and currents in the near-Earth plasma sheet and inner magnetosphere

The region occupying radial distances of \~3 - 9 Earth radii (RE) in the night side, includes the near-Earth plasma sheet with stretched magnetic field lines and the inner magnetosphere with strong dipolar magnetic field. In this region, the plasma flow energy, which was injected into the inner magnetosphere from the magnetotail, is converted to particle heating and electromagnetic wave generation. These important processes are controlled by plasma anisotropies, which are the focus of this study. Using measurements of THEMIS ...

Artemyev, A.; Zhang, X.-J.; Angelopoulos, V.; Runov, A.; Spence, H.; Larsen, B.;

YEAR: 2018     DOI: 10.1029/2018JA025232

injections; inner magnetosphere; plasma currents; plasma sheet; Van Allen Probes

Properties of intense field-aligned lower-band chorus waves: Implications for nonlinear wave-particle interactions

Resonant interactions between electrons and chorus waves are responsible for a wide range of phenomena in near-Earth space (e.g., diffuse aurora, acceleration of MeV electrons, etc.). Although quasi-linear diffusion is believed to be the primary paradigm for describing such interactions, an increasing number of investigations suggest that nonlinear effects are also important in controlling the rapid dynamics of electrons. However, present models of nonlinear wave-particle interactions, which have been successfully used to de ...

Zhang, X.-J.; Thorne, R.; Artemyev, A.; Mourenas, D.; Angelopoulos, V.; Bortnik, J.; Kletzing, C.; Kurth, W.; Hospodarsky, G.;

YEAR: 2018     DOI: 10.1029/2018JA025390

chorus waves; Effective amplitude; nonlinear wave-particle interaction; spatial distribution; statistics; Van Allen Probes; Wave-packet length

Rapid Enhancements of the Seed Populations in the Heart of the Earth\textquoterights Outer Radiation Belt: A Multicase Study

To better understand rapid enhancements of the seed populations (hundreds of keV electrons) in the heart of the Earth\textquoterights outer radiation belt (L* ~ 3.5\textendash5.0) during different geomagnetic activities, we investigate three enhancement events measured by Van Allen Probes in detail. Observations of the fluxes and the pitch angle distributions of energetic electrons are analyzed to determine rapid enhancements of the seed populations. Our study shows that three specified processes associated with substorm ele ...

Tang, C.; Xie, X.; Ni, B.; Su, Z.; Reeves, G.; Zhang, J.-C.; Baker, D.; Spence, H.; Funsten, H.; Blake, J.; Wygant, J.; . Y. Dai, G;

YEAR: 2018     DOI: 10.1029/2017JA025142

enhanced convection; Substorm Injections; the outer radiation belt; the seed population; ULF waves; Van Allen Probes

Electron nonlinear resonant interaction with short and intense parallel chorus wave-packets

One of the major drivers of radiation belt dynamics, electron resonant interaction with whistler-mode chorus waves, is traditionally described using the quasi-linear diffusion approximation. Such a description satisfactorily explains many observed phenomena, but its applicability can be justified only for sufficiently low intensity, long duration waves. Recent spacecraft observations of a large number of very intense lower band chorus waves (with magnetic field amplitudes sometimes reaching \~1\% of the background) therefore ...

Mourenas, D.; Zhang, X.-J.; Artemyev, A.; Angelopoulos, V.; Thorne, R.; Bortnik, J.; Neishtadt, A.; Vasiliev, A.;

YEAR: 2018     DOI: 10.1029/2018JA025417

chorus waves; ; kinetic equation; nonlinear interaction; Radiation belts; short wave-packets; trapping; Van Allen Probes

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

Comparing simulated and observed EMIC wave amplitudes using in situ Van Allen Probes\textquoteright measurements

We perform a statistical study calculating electromagnetic ion cyclotron (EMIC) wave amplitudes based off in situ plasma measurements taken by the Van Allen Probes\textquoteright (1.1\textendash5.8 Re) Helium, Oxygen, Proton, Electron (HOPE) instrument. Calculated wave amplitudes are compared to EMIC waves observed by the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes during the same period. The survey covers a 22-month period (1 November 2012 to 31 August 2014), a full Van ...

Saikin, A.A.; Jordanova, V.K.; Zhang, J.C.; Smith, C.W.; Spence, H.E.; Larsen, B.A.; Reeves, G.D.; Torbert, R.B.; Kletzing, C.A.; Zhelavskaya, I.S.; Shprits, Y.Y.;

YEAR: 2018     DOI: 10.1016/j.jastp.2018.01.024

EMIC waves Van Allen Probes Linear theory Wave generation; Van Allen Probes



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