Found 844 entries in the Bibliography.
Showing entries from 1 through 50
| 2021 |
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Origin of Electron Boomerang Stripes: Statistical Study Abstract In the outer radiation belt, localized ULF waves can interact with energetic electrons by drift resonance, leading to quasiperiodic oscillations. The oscillations in the pitch angle spectrum can be characterized by either boomerang-shaped or straight stripes. Previous studies have shown that boomerang-shaped stripes evolve from straight ones when electrons drift away from the localized wave interaction region. Based on the time-of-flight technique on the pitch angle-dependent drift velocity, the origin can be remote ... Zhao, X.; Hao, Y.; Zong, Q.; Zhou, X.; Yue, Chao; Chen, X.; Liu, Y.; Liu, Z.-Y.; Blake, J.; Claudepierre, S.; Reeves, G.; YEAR: 2021 DOI: https://doi.org/10.1029/2021GL093377 Localized ULF waves; Energetic Elctrons; drift resonance; Time-of-flight Technique; source region; boomerang-shaped stripes; Van Allen Probes |
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Abstract This paper presents results from a numerical study of the guiding of VLF whistler-mode waves along the ambient magnetic field by the shelf-like density structures observed by the NASA Van Allen Probes satellites in the equatorial plasmasphere. The shelf-duct consists of a homogeneous central part “sandwiched” between two density gradients pointing in the same direction. To the best of our knowledge, this type of whistler ducting has never been identified in observations before. Our investigation is based on simu ... YEAR: 2021 DOI: https://doi.org/10.1029/2021JA029403 Whistler waves; density duct; plasmasphere; RBSP; simulations; Van Allen Probes |
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A Multi-instrument Study of a Dipolarization Event in the Inner Magnetosphere Abstract A dipolarization of the background magnetic field was observed during a conjunction of the Magnetospheric Multiscale (MMS) spacecraft and Van Allen Probe B on 22 September 2018. The spacecraft were located in the inner magnetosphere at L ∼ 6 − 7 just before midnight magnetic local time (MLT). The radial separation between MMS and Probe B was ∼ 1RE. Gradual dipolarization or an increase of the northward component BZ of the background field occurred on a timescale of minutes. Exploration of energization and Radi ... Matsui, H.; Torbert, R.; Spence, H.; Argall, M.; Cohen, I.; Cooper, M.; Ergun, R.; Farrugia, C.; Fennell, J.; Fuselier, S.; Gkioulidou, M.; Khotyaintsev, Yu.; Lindqvist, P.-A.; Matsuoka, A.; Russell, C.; Shoji, M.; Strangeway, R.; Turner, D.; Vaith, H.; Wygant, J.; YEAR: 2021 DOI: https://doi.org/10.1029/2021JA029294 Dipolarization; inner magnetosphere; Multiple Scale Dynamics; Van Allen Probes |
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Abstract Radiation belt flux dropout events are sudden and often significant reductions in high-energy electrons from Earth’s outer radiation belts. These losses are theorized to be due to interactions with the dayside magnetopause and possibly connected to observations of escaping magnetospheric particles. This study focuses on radiation belt losses during a moderate-strength, nonstorm dropout event on 21 November 2016. The potential loss mechanisms and the linkage to dayside escape are investigated using combined energet ... Cohen, I.; Turner, D.; Michael, A.; Sorathia, K.; . Y. Ukhorskiy, A; YEAR: 2021 DOI: https://doi.org/10.1029/2021JA029261 Radiation belt; Magnetospheric escape; energetic electrons; Flux dropout events; test particle simulations; Van Allen Probes |
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A Statistical Study of Lower Hybrid Waves In the Earth’s Magnetosphere by Van Allen Probes Abstract The lower hybrid (LH) waves are electrostatic emissions near the LH resonant frequency. They propagate perpendicularly with a small wavelength comparable to Larmor radius of thermal particles and can heat both ions and electrons. In this paper, we statistically study the global distribution of LH waves in the inner magnetosphere by using Van Allen Probes observation from 2012 to 2018. We find that (1) LH waves are commonly observed in the inner magnetosphere. Most LH waves are confined near the magnetic equator with ... Liu, Xu; Chen, Lunjin; Ma, Qianli; YEAR: 2021 DOI: https://doi.org/10.1029/2021GL093168 |
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Rapid injections of MeV electrons and extremely fast step-like outer radiation belt enhancements Abstract Rapid injection of MeV electrons associated with strong substorm dipolarization has been suggested as a potential explanation for some radiation belt enhancement events. However, it has been difficult to quantify the contribution of MeV electron injections to radiation belt enhancements. This paper presents two isolated MeV electron injection events for which we quite precisely quantify how the entire outer-belt immediately changed with the injections. Tracking detailed outer-belt evolution observed by Van Allen Pro ... Kim, H.-J.; Lee, D.-Y.; Wolf, R.; Bortnik, J.; Kim, K.-C.; Lyons, L.; Choe, W.; Noh, S.-J.; Choi, K.-E.; Yue, C.; Li, J.; YEAR: 2021 DOI: https://doi.org/10.1029/2021GL093151 Radiation belt enhancement; Relatvistic electrons; substorm injection; Step-like; Extremely fast; Van Allen Probes |
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Abstract We performed a comprehensive statistical study of electromagnetic ion cyclotron (EMIC) waves observed by the Van Allen Probes and Exploration of energization and Radiation in Geospace satellite (ERG/Arase). From 2017 to 2018, we identified and categorized EMIC wave events with respect to wavebands (H+ and He+ EMIC waves) and relative locations from the plasmasphere (inside and outside the plasmasphere). We found that H+ EMIC waves in the morning sector at L>8 are predominantly observed with a mixture of linear and r ... Jun, C.-W; Miyoshi, Y.; Kurita, S.; Yue, C.; Bortnik, J.; Lyons, L.; Nakamura, S.; Shoji, M.; Imajo, S.; Kletzing, C.; Kasahara, Y.; Kasaba, Y.; Matsuda, S.; Tsuchiya, F.; Kumamoto, A.; Matsuoka, A.; Shinohara, I.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA029001 Spatial distributions of EMIC waves; RBSP and Arase observations; EMIC wave properties; EMIC wave dependence on geomagnetic condition; Van Allen Probes |
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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 |
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Abstract We compare ESA PROBA-V observations of electron flux at LEO with those from the NASA Van Allen Probes mostly at MEO for October 2013. Dropouts are visible at all energy during 4 storms from both satellites. Equatorial trapped electron fluxes are higher than at LEO by 102 (<1 MeV) to 105 (>2.5 MeV). We observe a quite isotropic structure of the outer belt during quiet times, contrary to the inner belt, and pitch angle dependence of high energy injection. We find very good overlap of the outer belt at MEO and LEO at ... Pierrard, V.; Ripoll, J.-F.; Cunningham, G.; Botek, E.; Santolik, O.; Thaller, S.; Kurth, W.; Cosmides, M.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028850 Radiation belts; relativistic electrons; Geomagnetic storms; energetic particles; Van Allen Probes |
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Abstract This paper examines the rapid losses and acceleration of trapped relativistic and ultrarelativistic electron populations in the Van Allen radiation belt during the September 7-9, 2017, geomagnetic storm. By analyzing the dynamics of the last closed drift shell (LCDS) and the electron flux and phase space density (PSD), we show that the electron dropouts are consistent with magnetopause shadowing and outward radial diffusion to the compressed LCDS. During the recovery phase an in-bound pass of Van Allen Probe A shows ... Olifer, L.; Mann, I.; Ozeke, L.; Morley, S.; Louis, H.; YEAR: 2021 DOI: https://doi.org/10.1029/2020GL092351 Van Allen Probes; magnetopause shadowing; ULF wave radial diffusion; electron phase space density |
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Sustained oxygen spectral gaps and their dynamic evolution in the inner magnetosphere Abstract Van Allen Probes observations of ion spectra often show a sustained gap within a very narrow energy range throughout the full orbit. To understand their formation mechanism, we statistically investigate the characteristics of the narrow gaps for oxygen ions and find that they are most frequently observed near the noon sector with a peak occurrence rate of over 30\%. The magnetic moment (μ) of the oxygen ions in the gap shows a strong dependence on magnetic local time (MLT), with higher and lower μ in the morning a ... Yue, Chao; Zhou, Xu-Zhi; Bortnik, Jacob; Zong, Qiu-Gang; Li, Yuxuan; Ren, Jie; Reeves, Geoffrey; Spence, Harlan; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA029092 oxygen spectral gaps; corotational drift resonance; sustained gaps; drainage void; test particle simulations; Van Allen Probes |
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Characteristics of low-harmonic magnetosonic waves in the Earth’s inner magnetosphere Abstract Magnetosonic (MS) waves are electromagnetic waves that play important roles in the acceleration and scattering of radiation belt electrons. However, previous statistical analyses of the global MS wave distribution were mainly restricted to magnetic field measurements. In this study, we first report a low-harmonic MS wave event observed only by the electric field instrument of Van Allen Probes. The MS wave frequencies follow the local proton gyrofrequency (fcp), which suggests the characteristics of nearly local gene ... Teng, S.; Liu, N.; Ma, Q.; Tao, X.; YEAR: 2021 DOI: https://doi.org/10.1029/2021GL093119 Low-frequency magnetosonic wave; wave generation; Magnetosonic wave spectra; Van Allen Probes |
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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 |
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Energetic electron detection packages on board Chinese navigation satellites in MEO Abstract Energetic electron measurements and spacecraft charging are of great significance for theoretical research in space physics and space weather applications. In this paper, the energetic electron detection package (EEDP) deployed on three Chinese navigation satellites in medium Earth orbit (MEO) is reviewed. The instrument was developed by the space science payload team led by Peking University. The EEDP includes a pinhole medium-energy electron spectrometer (MES), a high-energy electron detector (HED) based on ΔE-E ... YuGuang, Ye; Hong, Zou; Qiu-Gang, Zong; HongFei, Chen; JiQing, Zou; WeiHong, Shi; XiangQian, Yu; WeiYing, Zhong; YongFu, Wang; YiXin, Hao; ZhiYang, Liu; XiangHong, Jia; Bo, Wang; XiaoPing, Yang; XiaoYun, Hao; YEAR: 2021 DOI: https://doi.org/10.26464/epp2021021 Radiation belts; energetic electron detection; Pin-hole technology; Chinese navigation satellites; MEO; internal charging; Van Allen Probes |
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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 |
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Harmonization of RBSP and Arase energetic electron measurements utilizing ESA radiation monitor data Abstract Accurate measurements of trapped energetic electron fluxes are of major importance for the studies of the complex nature of radiation belts and the characterization of space radiation environment. The harmonization of measurements between different instruments increase the accuracy of scientific studies and the reliability of data-driven models that treat the specification of space radiation environment. An inter-calibration analysis of the energetic electron flux measurements of the Magnetic Electron Ion Spectromet ... Sandberg, I.; Jiggens, P.; Evans, H.; Papadimitriou, C.; Aminalragia–Giamini, S.; Katsavrias, Ch.; Boyd, A.; O’Brien, T.; Higashio, N.; Mitani, T.; Shinohara, I.; Miyoshi, Y.; Baker, D.; Daglis, I.; YEAR: 2021 DOI: https://doi.org/10.1029/2020SW002692 Radiation belt; calibration; data harmonization; space radiation environment; energetic electrons; Van Allen Probes |
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Abstract Geomagnetic substorms are major energy transfer events where energy stored in the Earths magnetotail is released into the ionosphere. Substorm phenomena, including auroral activities, earthward Poynting flux, magnetic field dipolarization, etc, have been extensively studied. However, the complex interplay among them is not fully understood. In a fortuitous event on June 07, 2013, the twin Van Allen Probes (separated by 0.4 hour in local time) observed bursts of earthward Alfvenic Poynting flux in the vicinity of the ... Tian, S.; Colpitts, C.; Wygant, J.; Cattell, C.; Ferradas, C.; Igl, A.; Larsen, B.; Reeves, G.; Donovan, E.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA029019 Poynting flux; auroral physics; discrete arc; Dipolarization; Alfven waves; Van Allen Probes |
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Upper limit of proton anisotropy and its relation to EMIC waves in the inner magnetosphere Abstract Proton anisotropy in velocity space has been generally accepted as a major parameter for exciting electromagnetic ion cyclotron (EMIC) waves. In this study, we estimate the proton anisotropy parameter as defined by the linear resonance theory using data from the Van Allen Probes mission. Our investigation uses the measurements of the inner magnetosphere (L < 6) from January 2013 to February 2018. We find that the proton anisotropy is always clearly limited by an upper bound and it well follows an inverse relationshi ... Noh, Sung-Jun; Lee, Dae-Young; Kim, Hyomin; Lanzerotti, Louis; Gerrard, Andrew; Skoug, Ruth; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028614 Proton Anisotropy; Ion cyclotron instability; Proton distribution; Van Allen Probes; Wave-particle interaction |
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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 |
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Abstract Isolated proton auroras (IPAs) appearing at subauroral latitudes are generated by energetic protons precipitating from the magnetosphere through interaction with electromagnetic ion cyclotron (EMIC) waves. An IPA thus indicates the spatial scale and temporal variation of wave–particle interactions in the magnetosphere. In this study, a unique event of simultaneous ground and magnetospheric satellite observations of two IPAs were conducted on March 16, 2015, using an all-sky imager at Athabasca, Canada and Van Alle ... Nakmaura, Kohki; Shiokawa, Kazuo; Otsuka, Yuichi; Shinbori, Atsuki; Miyoshi, Yoshizumi; Connors, Martin; Spence, Harlan; Reeves, Geoff; Funsten, Herbert; MacDowall, Robert; Smith, Charles; Wygant, John; Bonnell, John; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA029078 |
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Abstract With Van Allen Probes data, we present the observational support for whistler waves guided by the plasmapause based on a case study and statistical analyses. Due to the combined effects of inhomogeneous magnetic fields and plasma densities, whistler waves near the inner edge of plasmapause (plasmasphere side) will be guided by a HDD-like (HDD, high density duct) density gradient, and tend to have very small wave normal angles (WNAs ≤20°). In contrast, whistler waves around the outer edge of the plasmapause (plasm ... Chen, Rui; Gao, Xinliang; Lu, Quanming; Tsurutani, Bruce; Wang, Shui; YEAR: 2021 DOI: https://doi.org/10.1029/2021GL092652 Plasmapause; whistler wave; ducting effect; inner edge; outer edge; wave normal angle; Van Allen Probes |
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Whistler-mode waves trapped by density irregularities in the Earth s magnetosphere Abstract Whistler-mode waves are electromagnetic waves pervasively observed in the Earth s and other planetary magnetospheres. They are considered to be mainly responsible for producing the hazardous radiation and diffuse aurora, which heavily relies on their properties. Density irregularities, frequently observed in the Earth s magnetospheres, are found to change largely the properties of whistler-mode waves. Here we report, using Van Allen Probes measurements, whistler-mode waves strongly modulated by two different density ... Ke, Yangguang; Chen, Lunjin; Gao, Xinliang; Lu, Quanming; Wang, Xueyi; Chen, Rui; Chen, Huayue; Wang, Shui; YEAR: 2021 DOI: https://doi.org/10.1029/2020GL092305 WHISTLER-MODE WAVES; density irregularities; Magnetosphere; Radiation belts; particle-in-cell simulation; Wave trapping; Van Allen Probes |
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Prediction of Dynamic Plasmapause Location Using a Neural Network Abstract As a common boundary layer that distinctly separates the regions of high-density plasmasphere and low-density plasmatrough, the plasmapause is essential to comprehend the dynamics and variability of the inner magnetosphere. Using the machine learning framework Pytorch and high-quality Van Allen Probes data set, we develop a neural network model to predict the global dynamic variation of the plasmapause location, along with the identification of 6537 plasmapause crossing events during the period from 2012 to 2017. To ... Guo, DeYu; Fu, Song; Xiang, Zheng; Ni, Binbin; Guo, YingJie; Feng, Minghang; Guo, JianGuang; Hu, Zejun; Gu, Xudong; Zhu, Jianan; Cao, Xing; Wang, Qi; YEAR: 2021 DOI: https://doi.org/10.1029/2020SW002622 Plasmapause; neural network; Van Allen Probes; space weather forecast |
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Abstract This study considers the impact of electron precipitation from Earth s radiation belts on atmospheric composition using observations from the NASA Van Allen Probes and NSF Focused Investigations of Relativistic Electron Burst Intensity, Range, and Dynamics (FIREBIRD II) CubeSats. Ratios of electron flux between the Van Allen Probes (in near-equatorial orbit in the radiation belts) and FIREBIRD II (in polar low Earth orbit) during spacecraft conjunctions (2015-2017) allow an estimate of precipitation into the atmosph ... Duderstadt, K.; Huang, C.-L.; Spence, H.; Smith, S.; Blake, J.; Crew, A.; Johnson, A.; Klumpar, D.; Marsh, D.; Sample, J.; Shumko, M.; Vitt, F.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JD033098 electron precipitation; Radiation belts; ozone; Atmospheric Ionization; Van Allen Probes; FIREBIRD |
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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 |
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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 |
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Abstract Stable auroral red (SAR) arcs are optical events with dominant 630.0-nm emission caused by low-energy electron heat flux into the topside ionosphere from the inner magnetosphere. SAR arcs are observed at subauroral latitudes and often occur during the recovery phase of magnetic storms and substorms. Past studies concluded that these low-energy electrons were generated in the spatial overlap region between the outer plasmasphere and ring-current ions and suggested that Coulomb collisions between plasmaspheric electro ... Inaba, Yudai; Shiokawa, Kazuo; Oyama, Shin-Ichiro; Otsuka, Yuichi; Connors, Martin; Schofield, Ian; Miyoshi, Yoshizumi; Imajo, Shun; Shinbori, Atsuki; Gololobov, Artem; Kazama, Yoichi; Wang, Shiang-Yu; W. Y. Tam, Sunny; Chang, Tzu-Fang; Wang, Bo-Jhou; Asamura, Kazushi; Yokota, Shoichiro; Kasahara, Satoshi; Keika, Kunihiro; Hori, Tomoaki; Matsuoka, Ayako; Kasahara, Yoshiya; Kumamoto, Atsushi; Matsuda, Shoya; Kasaba, Yasumasa; Tsuchiya, Fuminori; Shoji, Masafumi; Kitahara, Masahiro; Nakamura, Satoko; Shinohara, Iku; Spence, Harlan; Reeves, Geoff; MacDowall, Robert; Smith, Charles; Wygant, John; Bonnell, John; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA029081 SAR arc; Arase; RBSP; ring current; Non-storm-time substorm; Plasmapause; Van Allen Probes |
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A comparative study on the distributions of incoherent and coherent plasmaspheric hiss Abstract We perform a comparative study on the distributions of incoherent and coherent plasmaspheric hiss, based on the Van Allen Probe data. The statistics show that incoherent hiss ( ∼10–20 pT) is widely distributed in dayside plasmasphere, with peak frequencies below 500 Hz; intense coherent hiss (amplitudes up to 80 pT) occurs in outer plasmasphere of L > 4 (L denotes the L-shell.), whose frequency increases with ambient magnetic field significantly. The Poynting flux analysis indicates that incoherent hiss generall ... He, Zhaoguo; Yu, Jiang; Li, Kun; Liu, Nigang; Chen, Zewen; Cui, Jun; YEAR: 2021 DOI: https://doi.org/10.1029/2021GL092902 |
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In situ Observations of Whistler-mode Chorus Waves Guided by Density Ducts Abstract In this paper, we report the proof of the existence of density ducts in the Earth’s magnetosphere by studying in situ observations of whistler-mode chorus waves using NASA’s Van Allen Probe-A data. Chorus waves, originally excited inside the density ducts with wave normal angles (WNAs) smaller than the Gendrin angle at near equator region, are efficiently confined to a limited area inside density ducts (i.e., ducted regions), and remain with small WNAs as they propagate towards high latitudes. The ducted region ... Chen, Rui; Gao, Xinliang; Lu, Quanming; Chen, Lunjin; Tsurutani, Bruce; Li, Wen; Ni, Binbin; Wang, Shui; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028814 Radiation belt; Chorus wave; density duct; ducted region; Van Allen Probes |
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Abstract We have conducted a statistical study of toroidal mode standing Alfvén waves detected by the Van Allen Probes spacecraft in the dayside inner magnetosphere, with an emphasis on the nodal structure of the fundamental through fifth harmonics. We developed a technique to accurately assign harmonic mode numbers to peaks in the power spectra of the electric (Eν) and magnetic (Bϕ) field components of toroidal waves and then determine the spectral intensities of Eν and Bϕ and the coherence and cross-phase between thes ... Takahashi, Kazue; Denton, Richard; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028981 Toroidal Alfven waves; inner magnetosphere; Nodal structure; Field line mass density distribution; Van Allen Probes |
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Abstract The impact of radial diffusion in storm time radiation belt dynamics is well-debated. In this study we quantify the changes and variability in radial diffusion coefficients during geomagnetic storms. A statistical analysis of Van Allen Probes data (2012 − 2019) is conducted to obtain measurements of the magnetic and electric power spectral densities for Ultra Low Frequency (ULF) waves, and corresponding radial diffusion coefficients. The results show global wave power enhancements occur during the storm main phase ... Sandhu, J.; Rae, I.; Wygant, J.; Breneman, A.; Tian, S.; Watt, C.; Horne, R.; Ozeke, L.; Georgiou, M.; Walach, M.-T.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA029024 ULF waves; radial diffusion; outer radiation belt; Van Allen Probes; Geomagnetic storms |
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Abstract We present, for the first time, a plasmaspheric hiss event observed by the Van Allen probes in response to two successive interplanetary shocks occurring within an interval of ∼2 hours on December 19, 2015. The first shock arrived at 16:16 UT and caused disappearance of hiss for ∼30 minutes. Combined effect of plasmapause crossing, significant Landau damping by suprathermal electrons and their gradual removal by magnetospheric compression led to the disappearance of hiss. Calculation of electron phase space dens ... Chakraborty, S.; Chakrabarty, D.; Reeves, G.; Baker, D.; Claudepierre, S.; Breneman, A.; Hartley, D.; Larsen, B.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028873 Plasmaspheric Hiss; Van Allen Probe; Interplanetary shocks; substorms; Whistlers; ULF waves; Van Allen Probes |
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A Comparison of the Location of the Mid-latitude Trough and Plasmapause Boundary Abstract We have compared the location of the mid-latitude trough observed in two dimensional vertical total electron content (vTEC) maps with four plasmapause boundary models, Radiation Belt Storm Probes observations, and IMAGE EUV observations all mapped to the ionosphere pierce point using the Tsyganenko [1996] magnetic field line model. For this study we examine four events over North America: one just after the 13 October 2012 storm, one during the 20 April 2002 double storm, another during a large substorm on 26 Januar ... Weygand, J.M.; Zhelavskaya, I.; Shprits, Y.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028213 mid-latitude trough; plasmapause boundary; vTECs; plasmapause models; Van Allen Probes |
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Formation of the mass density peak at the magnetospheric equator triggered by EMIC waves Abstract We report a simultaneous observation of two band electromagnetic ion cyclotron (EMIC) waves and toroidal Alfvén waves by the Van Allen Probe mission. Through wave frequency analyses, the mass density ρ is found to be locally peaked at the magnetic equator. Perpendicular fluxes of ions (< 100 eV) increase simultaneously with the appearances of EMIC waves, indicating a heating of these ions by EMIC waves. In addition, the measured ion distributions also support the equatorial peak formation, which accords with the r ... Xue, Zuxiang; Yuan, Zhigang; Yu, Xiongdong; Shiyong, Huang; Qiao, Zheng; YEAR: 2021 DOI: https://doi.org/10.26464/epp2021008 Toroidal Alfven waves; EMIC waves; magnetoseismology; equatorial mass density peak; Van Allen Probes |
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Abstract We evaluate the location, extent and energy range of electron precipitation driven by ElectroMagnetic Ion Cyclotron (EMIC) waves using coordinated multi-satellite observations from near-equatorial and Low-Earth-Orbit (LEO) missions. Electron precipitation was analyzed using the Focused Investigations of Relativistic Electron Burst Intensity, Range and Dynamics (FIREBIRD-II) CubeSats, in conjunction either with typical EMIC-driven precipitation signatures observed by Polar Orbiting Environmental Satellites (POES) or ... Capannolo, L.; Li, W.; Spence, H.; Johnson, A.; Shumko, M.; Sample, J.; Klumpar, D.; YEAR: 2021 DOI: https://doi.org/10.1029/2020GL091564 electron precipitation; EMIC waves; inner magnetosphere; electron losses; proton precipitation; wave-particle interactions; Van Allen Probes |
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Reconstruction of the Radiation Belts for Solar Cycles 17 – 24 (1933 – 2017) AbstractWe present a reconstruction of the dynamics of the radiation belts from Solar Cycles 17 – 24 which allows us to study how radiation belt activity has varied between the different solar cycles. The radiation belt simulations are produced using the Versatile Electron Radiation Belt (VERB)-3D code. The VERB-3D code simulations incorporate radial, energy, and pitch angle diffusion to reproduce the radiation belts. Our simulations use the historical measurements of Kp (available since Solar Cycle 17, i.e., 1933) to mode ... Saikin, A.; . Y. Shprits, Y; . Y. Drozdov, A; Landis, D.; Zhelavskaya, I.; Cervantes, S.; YEAR: 2021 DOI: https://doi.org/10.1029/2020SW002524 Radiation belts; numerical modeling; Particle acceleration; Magnetosphere: inner; forecasting; Van Allen Probes |
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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 |
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A Case Study of Transversely Heated Low-Energy Helium Ions by EMIC Waves in the Plasmasphere Abstract The Van Allen Probe A spacecraft observed strong ∼0.5-Hz helium (He+) band and weak ∼0.8-Hz hydrogen (H+) band EMIC waves on April 17, 2018, at L = ∼4.5–5.2, in the dawn sector, near the magnetic equator, and close to the plasmapause. We examined low-energy ion fluxes observed by the Helium Oxygen Proton and Electron (HOPE) instrument onboard Van Allen Probe A during the wave interval and found that low-energy He+ flux (<10 eV) enhancements occur nearly simultaneously with He-band and H-band EMIC wave pow ... Kim, Khan-Hyuk; Kwon, Hyuck-Jin; Lee, Junhyun; Jin, Ho; Seough, Jungjoon; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028560 |
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Periodic Rising and Falling Tone ECH Waves from Van Allen Probes Observations AbstractElectron cyclotron harmonic (ECH) waves are known to precipitate plasma sheet electrons into the upper atmosphere and generate diffuse aurorae. In this study, we report quasi-periodic rising (3 events) and falling tone (22 events) ECH waves observed by Van Allen Probes, and evaluate their properties. These rising and falling tone ECH waves prefer to occur during quiet geomagnetic conditions over the dusk to midnight sector in relatively high-density (10–80 cm-3) regions. Their repetition periods increase with incre ... Shen, Xiao-Chen; Li, Wen; Ma, Qianli; YEAR: 2021 DOI: https://doi.org/10.1029/2020GL091330 ECH wave; falling tone; rising tone; Magnetosphere; plasma wave; Van Allen Probes |
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Abstract We study packages of VLF whistler-mode waves observed by the Van Allen Probes satellites in the equatorial plasmasphere. We demonstrate that the main mechanism providing localization of these waves inside relatively broad (>1 RE across the ambient magnetic field) magnetospheric regions is a combined effect of the transverse gradients in the plasma density and the ambient magnetic field. The criterion for the wave trapping by these gradients is the same as for the wave trapping inside a high-density duct with a symme ... YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028933 density inhomogeneity; duct; Plasmapause; plasmasphere; VLF waves; whistler; Van Allen Probes |
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Abstract During geomagnetic storms, magnetospheric wave activity drives the ion precipitation which can become an important source of energy flux into the ionosphere and strongly affect the dynamics of the magnetosphere-ionosphere coupling. In this study, we investigate the role of Electro Magnetic Ion Cyclotron (EMIC) waves in causing ion precipitation into the ionosphere using simulations from the RAM-SCBE model with and without EMIC waves included. The global distribution of H-band and He-band EMIC wave intensity in the m ... Shreedevi, P.; Yu, Yiqun; Ni, Binbin; Saikin, Anthony; Jordanova, Vania; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028553 EMIC waves; Geomagnetic storms; proton precipitation; ring current modeling; MI coupling; wave particle interaction; Van Allen Probes |
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Abstract In this paper, analytical approximation is used to solve the wave equations near the plasmapause boundary layer in order to examine the validity of ray tracing approach for fast magnetosonic (MS) wave propagations, and then analytical solutions for electromagnetic fields of MS waves through the plasmapause boundary layer are provided for the first time. Both theoretical calculations from the analytical expressions and observations of Van Allen Probes have indicated that electric fields of MS waves decrease rapidly b ... Yu, Xiongdong; Yuan, Zhigang; Ouyang, Zhihai; Yao, Fei; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028330 MS waves; Radial propagation; Analytical approach; WKB approximation; Van Allen Probes |
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RBSP-ECT Combined Pitch Angle Resolved Electron Flux Data Product Abstract We describe a new data product combining pitch angle resolved electron flux measurements from the Radiation Belt Storm Probes (RBSP) Energetic Particle Composition and Thermal Plasma (ECT) suite on the National Aeronautics and Space Administration s Van Allen Probes. We describe the methodology used to combine each of the data sets and produce a consistent set of pitch-angle-resolved spectra for the entire Van Allen Probes mission. Three-minute-averaged flux spectra are provided spanning energies from 15 eV up to 20 ... Boyd, A.J.; Spence, H.E.; Reeves, G.D.; Funsten, H.O; Skoug, R.K.; Larsen, B.A.; Blake, J.B.; Fennell, J.F.; Claudepierre, S.G.; Baker, D.N.; Kanekal, S.K.; Jaynes, A.N.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028637 |
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Abstract We present a statistical study of density cavities observed in the inner magnetosphere by the Van Allen Probes during four one-month periods: February 2013, July 2013, January 2014 and June 2014. These periods were chosen to allow the survey of all magnetic local times. We find that density cavities are a recurrent feature of the density profiles of in situ measurements in the inner magnetosphere. We further investigate the correlation between the density cavities and the enhancement of fluxes of warm ions with ener ... Ferradas, C.; Boardsen, S.; Fok, M.-C.; Buzulukova, N.; Reeves, G.; Larsen, B.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028326 Magnetosphere: inner; plasmasphere; magnetospheric configuration and dynamics; plasma waves and instabilities; plasma sheet; density cavity; cold ion heating; cold ions; warm Plasma cloak; Van Allen Probes |
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AbstractIn-situ electron density profiles obtained from Arase in the night magnetic local time (MLT) sector and from RBSP-B covering all MLTs are used to study the small-scale density irregularities present in the plasmasphere and near the plasmapause. Electron density perturbations with amplitudes > 10\% from background density and with time-scales less than 30-min are investigated here as the small-scale density irregularities. The statistical survey of the density irregularities is carried out using nearly two years of de ... Thomas, Neethal; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Kasahara, Yoshiya; Shinohara, Iku; Kumamoto, Atsushi; Tsuchiya, Fuminori; Matsuoka, Ayako; Kasahara, Satoshi; Yokota, Shoichiro; Keika, Kunihiro; Hori, Tomo; Asamura, Kazushi; Wang, Shiang-Yu; Kazama, Yoichi; Tam, Sunny; Chang, Tzu-Fang; Wang, Bo-Jhou; Wygant, John; Breneman, Aaron; Reeves, Geoff; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA027917 Electron density; small-scale density irregularities; plasmasphere; inner magnetosphere; Van Allen Probes; Arase |
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The First Observation of N+ Electromagnetic Ion Cyclotron Waves Abstract Observations from past space missions report on the significant abundance of N+, in addition to those of O+, outflowing from the terrestrial ionosphere and populating the near-Earth region. However, instruments on board current space missions lack the mass resolution to distinguish between the two, and often the role of N+ in regulating the magnetosphere dynamics, is lumped together with that of O+ ions. For instance, our understanding regarding the role of electromagnetic ion cyclotron (EMIC) waves in controlling t ... YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028716 electromagnetic ion cyclotron waves; heavy ions; Van Allen Probes; N+ EMIC Wave; Wave-particle interaction; inner magnetosphere |
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A combined neural network- and physics-based approach for modeling plasmasphere dynamics AbstractIn recent years, feedforward neural networks (NNs) have been successfully applied to reconstruct global plasmasphere dynamics in the equatorial plane. These neural network-based models capture the large-scale dynamics of the plasmasphere, such as plume formation and erosion of the plasmasphere on the nightside. However, their performance depends strongly on the availability of training data. When the data coverage is limited or non-existent, as occurs during geomagnetic storms, the performance of NNs significantly de ... Zhelavskaya, I.; Aseev, N.; . Y. Shprits, Y; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028077 plasmasphere; plasma density; neural networks; data assimilation; Kalman Filter; Machine learning; Van Allen Probes |
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Challenging the Use of Ring Current Indices During Geomagnetic Storms Abstract The ring current experiences dramatic enhancements during geomagnetic storms, however understanding the global distribution of ring current energy content is restricted by spacecraft coverage. Many studies use ring current indices as a proxy for energy content, but these indices average over spatial variations and include additional contributions. We have conducted an analysis of Van Allen Probes’ data, identifying the spatial distribution and storm-time variations of energy content. Ion observations from the HOPE ... Sandhu, J.; Rae, I.; Walach, M.-T.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028423 ring current; Geomagnetic storms; Van Allen Probes; inner magnetosphere; substorms |
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Abstract Energy spectra of ring current protons are crucial to understanding the ring current dynamics. Based on high-quality Van Allen Probes RBSPICE measurements, we investigate the global distribution of the reversed proton energy spectra using the 2013-2019 RBSPICE datasets. The reversed proton energy spectra are characterized by the distinct flux minima around 50 - 100 keV and flux maxima around 200 - 400 keV. Our results show that the reversed proton energy spectrum is prevalent inside the plasmasphere, with the occurr ... Juan, Yi; Song, Fu; Binbin, Ni; Xudong, Gu; Hua, Man; Xiang, Zheng; Cao, Xing; Shi, Run; Zhao, Yiwen; YEAR: 2021 DOI: https://doi.org/10.1029/2020GL091559 |
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Abstract We analyzed the magnetospheric global response to dynamic pressure pulses (DPPs) using the Heliophysics System Observatory (HSO) and ground magnetometers. During northward Interplanetary Magnetic Field (IMF) Bz conditions, the magnetosphere acts as a closed “cavity” and reacts to solar wind DPPs more simply than during southward IMF. In this study we use solar wind data collected by ACE and WIND together with magnetic field observations of Geotail, Cluster, THEMIS, MMS, Van Allen Probes, GOES missions, and groun ... Vidal-Luengo, S.; Moldwin, M.; YEAR: 2021 DOI: https://doi.org/10.1029/2020JA028587 Multi-satellite; Heliophysics System Observatory; Dynamic Pressure Pulse; Heliophysics; Magnetosphere; Van Allen Probes |
