Dominant Roles of High Harmonics on Interactions Between AKR and Radiation Belt Relativistic Electrons
作者：
Zhang, Sai;Shang, Xiongjun;He, Yihua;Liu, Si* ;Xiao, Fuliang*
期刊：
GEOPHYSICAL RESEARCH LETTERS ,2020年47(16):e2020GL088421-null ISSN：0094-8276
通讯作者：
Liu, Si;Xiao, Fuliang
作者机构：
[Liu, S; Xiao, Fuliang; Shang, Xiongjun; Zhang, Sai; He, Yihua; Liu, Si] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Peoples R China.;[Liu, S; Xiao, Fuliang; Zhang, Sai; Liu, Si] Changsha Univ Sci & Technol, Hunan Prov Higher Educ Key Lab Modeling & Monitor, Changsha, Peoples R China.
通讯机构：
[Liu, S; Xiao, FL] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Peoples R China.;Changsha Univ Sci & Technol, Hunan Prov Higher Educ Key Lab Modeling & Monitor, Changsha, Peoples R China.
关键词：
AKR;high harmonic order;dominant role;radiation belt electron
摘要：
Auroral kilometric radiations (AKR) are widely existing superluminous waves in the magnetosphere. Due to rarely available measurements of AKR magnetic field components, we derive the explicit expression of diffusion coefficients in terms of electric field components, which can be applied to various space plasma waves. Using Van Allen Probes data, we calculate diffusion coefficients with different harmonic orders for two AKR events. It is found that the first (higher) harmonic order contributes to diffusion coefficients at small (larger) pitch angles. The effect of higher harmonic orders becomes more significant as the electron energy increases. These results are contrary to the case of chorus wave, in which the first order usually contributes much to wave-particle interactions. Estimations show that the phase space density of 0.5 MeV electrons can increase ∼10 times within 6 hr by AKR. This study is important for better modeling of AKR-induced radiation belt electron dynamics. ©2020. American Geophysical Union. All Rights Reserved.
语种：
英文
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Upward propagation of lightning-generated whistler waves into the radiation belts
作者：
MingYue Guo;QingHua Zhou;FuLiang Xiao;Si Liu;YiHua He;...
期刊：
Science China Technological Sciences ,2020年63(2):243-248 ISSN：1674-7321
通讯作者：
Xiao, F.L.
作者机构：
[MingYue Guo; QingHua Zhou; FuLiang Xiao; Si Liu; YiHua He; Chang Yang] School of Physics and Electronic Sciences, Changsha University of Science and Technology, Changsha, China
通讯机构：
School of Physics and Electronic Sciences, Changsha University of Science and Technology, Changsha, China
关键词：
lightning-generated whistler waves;numerical simulation;radiation belts
摘要：
Lightning-generated whistler (LGW) waves which induce energetic electron precipitation provide an important coupling between the ionosphere and radiation belts. Using the ray-tracing technique, we examine the propagation behaviour of LGW waves and show that they can travel upward into the radiation belts during higher geomagnetic activities due to the plasmapause inward compression, particularly in cases of lower wave frequencies, lower wave normal angles and azimuthal angles. Both perpendicular and parallel group velocities of LGW waves remain in relatively small values inside the plasmasphere but change rapidly to high values outside the plasmasphere. The launching latitude increases with increasing LGW wave normal angle. These results here further reveal a detailed picture on how LGW waves escape out of the plasmasphere and onto the radiation belts. © 2019, Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature.
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英文
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Unusual Loss of Van Allen Belt Relativistic Electrons by Extremely Low-Frequency Chorus
作者：
Liu, Si;Xie, Yanqiong;Zhang, Sai;Shang, Xiongjun;Yang, Chang;...
期刊：
GEOPHYSICAL RESEARCH LETTERS ,2020年47(18):e2020GL089994- ISSN：0094-8276
通讯作者：
Xiao, Fuliang
作者机构：
[Shang, Xiongjun; Yang, Chang; Zhang, Sai; Xiao, Fuliang; Liu, Si; Zhou, Qinghua; He, Yihua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Peoples R China.;[Xiao, Fuliang; Liu, Si] Changsha Univ Sci & Technol, Hunan Prov Higher Educ Key Lab Modeling & Monitor, Changsha, Peoples R China.;[Xie, Yanqiong] Natl Univ Def Technol, Coll Meteorol & Oceanog, Nanjing, Peoples R China.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Peoples R China.;Changsha Univ Sci & Technol, Hunan Prov Higher Educ Key Lab Modeling & Monitor, Changsha, Peoples R China.
摘要：
Chorus waves with the frequency usually between 0.1 and 0.8 equatorial electron gyrofrequency fce can accelerate energetic electrons to relativistic energies (several mega-electron volts, MeV). Here, we report a unique event that both regular chorus and unusual chorus with extremely low frequency (ELF) below 0.1 fce occurred during the 22 December 2014 geomagnetic storm. Relativistic electron fluxes decreased with decreasing wave frequency and had minima exactly corresponding to the presence of ELF chorus. Performing a two-dimensional simulation, we find that ELF chorus can result in unusual loss of relativistic electrons while regular chorus contributes to the acceleration, leading to the frequency-modulated fluxes of such high-energy electrons. The current results provide a new scenario that ELF chorus waves can potentially mitigate space weather by inhibiting relativistic electron flux enhancements. ©2020. American Geophysical Union. All Rights Reserved.
语种：
英文
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Excitation of Highly Oblique Lower Band and Upper Band Chorus by a Loss Cone Feature and Temperature Anisotropy Distribution
作者：
Zhou, Qinghua;Yang, Chang;He, Yihua;Liu, Si;Gao, Zhonglei;...
期刊：
GEOPHYSICAL RESEARCH LETTERS ,2019年46(4):1929-1936 ISSN：0094-8276
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; Xiao, Fuliang; Gao, Zhonglei; Zhou, Qinghua; He, Yihua; Liu, Si] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Xiao, Fuliang; Zhou, Qinghua] Changsha Univ Sci & Technol, Hunan Prov Key Lab Flexible Elect Mat Genome Engn, Changsha, Hunan, Peoples R China.;[Xiao, Fuliang; Zhou, Qinghua] Changsha Univ Sci & Technol, Hunan Prov Higher Educ Key Lab Modeling & Monito, Changsha, Hunan, Peoples R China.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;Changsha Univ Sci & Technol, Hunan Prov Key Lab Flexible Elect Mat Genome Engn, Changsha, Hunan, Peoples R China.;Changsha Univ Sci & Technol, Hunan Prov Higher Educ Key Lab Modeling & Monito, Changsha, Hunan, Peoples R China.
关键词：
highly oblique chorus;wave-particle interaction;RBSP results;radiation belts
摘要：
Recent studies have indicated that highly oblique lower band chorus could be excited by temperature anisotropy with a low-energy electron plateau. Here we present another excitation mechanism of highly oblique lower and upper band chorus by using the simultaneous observations and numerical modeling. During 23:00–24:00UT on 3 July 2016, Van Allen probe A observed chorus with the wave normal angle close to the resonance cone both in the lower and upper bands around L=5.0 and MLT=3. Enhanced flux and pitch angle anisotropy of energetic electrons were observed in the same spatial region. Calculations of chorus growth rates show that highly oblique chorus waves can be excited by the energetic electrons with a loss cone feature and distinct temperature anisotropy, particularly more efficient in the presence of a low-energy plateau. The temperature anisotropy for the oblique upper band is higher than that for the lower band. ©2019. American Geophysical Union. All Rights Reserved.
语种：
英文
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Global Occurrences of Electrostatic Electron Cyclotron Harmonic Waves Associated With Radiation Belt Electron Distributions
作者：
Chen, Yaru;Zhou, Qinghua;He, Yihua;Yang, Chang;Liu, Si;...
期刊：
GEOPHYSICAL RESEARCH LETTERS ,2019年46(10):5028-5033 ISSN：0094-8276
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; Chen, Yaru; Xiao, Fuliang; Gao, Zhonglei; Zhou, Qinghua; He, Yihua; Liu, Si] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Chen, Yaru; Xiao, Fuliang; Zhou, Qinghua] Changsha Univ Sci & Technol, Hunan Prov Key Lab Flexible Elect Mat Genome Engn, Changsha, Hunan, Peoples R China.;[Chen, Yaru; Xiao, Fuliang; Zhou, Qinghua] Changsha Univ Sci & Technol, Hunan Prov Higher Educ Key Lab Modeling & Monitor, Changsha, Hunan, Peoples R China.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;Changsha Univ Sci & Technol, Hunan Prov Key Lab Flexible Elect Mat Genome Engn, Changsha, Hunan, Peoples R China.;Changsha Univ Sci & Technol, Hunan Prov Higher Educ Key Lab Modeling & Monitor, Changsha, Hunan, Peoples R China.
关键词：
Electrostatic electron cyclotron harmonic waves;electron ring distribution;global occurrences;radiation belt;Van Allen Probe observation
摘要：
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 1 October 2012 to 30 June 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 higher occurrence in the region of L = 5–6 and 06–19 MLT. The electron phase space density exhibits a distinct ring distribution (∂f/∂v⊥ > 0) with the peak energy around a few kiloelectron volts. Both ECH wave events and the electron ring distributions are closely related and tend to be more distinct with increasing geomagnetic activity. ©2019. American Geophysical Union. All Rights Reserved.
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英文
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Global Occurrences of Auroral Kilometric Radiation Related to Suprathermal Electrons in Radiation Belts
作者：
Zhao, Wanli;Liu, Si;Zhang, Sai;Zhou, Qinghua;Yang, Chang;...
期刊：
GEOPHYSICAL RESEARCH LETTERS ,2019年46(13):7230-7236 ISSN：0094-8276
通讯作者：
Xiao, Fuliang
作者机构：
[Zhao, Wanli; Yang, Chang; Zhang, Sai; Xiao, Fuliang; Gao, Zhonglei; Liu, Si; Zhou, Qinghua; He, Yihua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Zhao, Wanli; Xiao, Fuliang] Changsha Univ Sci & Technol, Hunan Prov Higher Educ Key Lab Modeling & Monitor, Changsha, Hunan, Peoples R China.;[Zhao, Wanli; Xiao, Fuliang] Changsha Univ Sci & Technol, Hunan Prov Key Lab Flexible Elect Mat Genome Engn, Changsha, Hunan, Peoples R China.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;Changsha Univ Sci & Technol, Hunan Prov Higher Educ Key Lab Modeling & Monitor, Changsha, Hunan, Peoples R China.;Changsha Univ Sci & Technol, Hunan Prov Key Lab Flexible Elect Mat Genome Engn, Changsha, Hunan, Peoples R China.
关键词：
auroral kilometric radiation;suprathermal electron flux enhancements;global occurrence;radiation belt
摘要：
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= 3–6.5 and 00–24 magnetic local time (MLT), with a higher occurrence on the nightside (20–24 MLT and 00–04 MLT) within L= 5–6.5. All the AKR events are observed to be accompanied with suprathermal (∼1 keV) electron flux enhancements. During active geomagnetic periods, both AKR occurrences and electron injections tend to be more distinct, and AKR emission extends to the dayside. The current study shows that AKR emissions from the remote sources are closely associated with electron injections. © 2019. American Geophysical Union. All Rights Reserved.
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英文
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Quantifying Extremely Rapid Flux Enhancements of Radiation Belt Relativistic Electrons Associated With Radial Diffusion
作者：
Liu, Si;Yan, Qi;Yang, Chang;Zhou, Qinghua;He, Zhaoguo;...
期刊：
GEOPHYSICAL RESEARCH LETTERS ,2018年45(3):1262-1270 ISSN：0094-8276
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; Xiao, Fuliang; Gao, Zhonglei; Liu, Si; Zhou, Qinghua; He, Yihua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Liu, Si; He, Zhaoguo] Univ Texas Dallas, Dept Phys, William B Hanson Ctr Space Sci, Richardson, TX 75083 USA.;[Yan, Qi] Macau Univ Sci & Technol, Lunar & Planetary Sci Lab, Macau, Peoples R China.;[He, Zhaoguo] Harbin Inst Technol, Shenzhen Grad Sch, Shenzhen, Peoples R China.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.
关键词：
radial diffusion;chorus-driven acceleration;radiation belt;Van Allen Probes;THEMIS
摘要：
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 2–3 October 2013 storm when Van Allen Probes observed extremely rapid (by about 50 times in 2h) flux enhancements of relativistic (1.8–3.4MeV) electrons but without distinct chorus at lower L-shells. Meanwhile, Time History of Events and Macroscale Interactions during Substorms satellites simultaneously measured enhanced chorus and fluxes of energetic (∼100–300keV) seed electrons at higher L-shells. Numerical calculations show that chorus can efficiently accelerate seed electrons at L ∼ 8.3. Then radial diffusion further increased the phase space density of relativistic electrons throughout the outer radiation belts, with a remarkable agreement with the observation in magnitude and timescale. The current results provide a different physical scenario on the interplay between radial diffusion and local acceleration in outer radiation belt. ©2018. American Geophysical Union. All Rights Reserved.
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英文
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Generation of Lower L Shell Dayside Chorus by Energetic Electrons From the Plasma Sheet
作者：
He, Yihua* ;Xiao, Fuliang* ;Su, Zhenpeng;Zheng, Huinan;Yang, Chang;...
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS ,2018年123(10):8109-8121 ISSN：2169-9380
通讯作者：
He, Yihua;Xiao, Fuliang
作者机构：
[Su, Zhenpeng; Zheng, Huinan; He, Yihua] Univ Sci & Technol China, Dept Geophys & Planetary Sci, CAS Key Lab Geospace Environm, Hefei, Anhui, Peoples R China.;[Yang, Chang; Xiao, Fuliang; He, Yihua; Liu, Si; Zhou, Qinghua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Su, Zhenpeng; Zheng, Huinan; He, Yihua] Univ Sci & Technol China, Collaborat Innovat Ctr Astronaut Sci & Technol, Hefei, Anhui, Peoples R China.;[He, Yihua] Univ Sci & Technol China, Sch Earth & Space Sci, Mengcheng Natl Geophys Observ, Hefei, Anhui, Peoples R China.
通讯机构：
[He, Yihua] U;[He, YH; Xiao, FL] C;Univ Sci & Technol China, Dept Geophys & Planetary Sci, CAS Key Lab Geospace Environm, Hefei, Anhui, Peoples R China.;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;Univ Sci & Technol China, Collaborat Innovat Ctr Astronaut Sci & Technol, Hefei, Anhui, Peoples R China.
关键词：
Van Allen Probes;dayside chorus generation;radiation belt;wave-particle interaction
摘要：
Currently, the generation mechanism for the lower L shell dayside chorus has still remained an open question. Here we report two storm events: 6–7 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 plasma sheet and drifted from midnight through dawn toward the dayside. Calculations of chorus local growth rates under different waves normal angles show that the upper cutoff and peak wave frequencies display similar patterns to the observations. Chorus growth rates maximize for the parallel propagation and drop with increasing wave normal angles. The current results confirm that the observed lower L shell dayside chorus can be excited by anisotropic electrons originating from the plasma sheet in drifting from the nightside to the dayside.
语种：
英文
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Storm Time Evolution of Outer Radiation Belt Relativistic Electrons by a Nearly Continuous Distribution of Chorus
作者：
Yang, Chang;Xiao, Fuliang* ;He, Yihua;Liu, Si;Zhou, Qinghua;...
期刊：
GEOPHYSICAL RESEARCH LETTERS ,2018年45(5):2159-2167 ISSN：0094-8276
通讯作者：
Xiao, Fuliang
作者机构：
[Zhao, Wanli; Yang, Chang; Xiao, Fuliang; He, Yihua; Liu, Si; Zhou, Qinghua; Guo, Mingyue] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Yang, Chang; He, Yihua] Univ Sci & Technol China, Dept Geophys & Planetary Sci, Hefei, Anhui, Peoples R China.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.
关键词：
outer radiation belt;whistler mode chorus wave;energetic electron;wave-particle interaction;geomagnetic storm
摘要：
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 magnetic local time = 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 MeV) electrons during two intervals when Probe A passed the location L = 4.3 along its orbit. The simulating results show that chorus with combined quasi-parallel and oblique components can produce a more pronounced flux enhancement in the pitch angle range ∼45°–80°, consistent well with the observation. The current results provide the first evidence on how relativistic electron fluxes vary under the drive of almost continuously distributed chorus with both quasi-parallel and oblique components within a complete orbit of Van Allen Probe.<br/> ©2018. American Geophysical Union. All Rights Reserved.
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英文
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Generation of extremely low frequency chorus in Van Allen radiation belts
作者：
Xiao, Fuliang* ;Liu, Si;Tao, Xin;Su, Zhenpeng;Zhou, Qinghua;...
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS ,2017年122(3):3201-3211 ISSN：2169-9380
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; Liu, Si; He, Yihua; Xiao, Fuliang; Zhou, Qinghua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Tao, Xin; Su, Zhenpeng; Gao, Zhonglei] Univ Sci & Technol China, Chinese Acad Sci, Key Lab Basic Plasma Phys, Hefei, Peoples R China.;[He, Zhaoguo] Harbin Inst Technol, Shenzhen Grad Sch, Shenzhen, Peoples R China.;[Baker, D. N.] Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.;[Spence, H. E.] Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.
关键词：
ELF chorus waves;wave-particle interaction;relativistic distribution;RBSP results
摘要：
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's 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, relativistic effects should be considered in the formula for whistler mode wave growth rate. Here we report high-resolution observations during the 14 October 2014 small storm and firstly demonstrate, using a fully relativistic simulation, that electrons with the high-energy tail population and relativistic pitch angle anisotropy can provide free energy sufficient for generating chorus below 0.1 fce. The simulated wave growth displays a very similar pattern to the observations. The current results can be applied to Jupiter, Saturn, and other magnetized planets.
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英文
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Generation of lower and upper bands of electrostatic electron cyclotron harmonic waves in the Van Allen radiation belts
作者：
Zhou, Qinghua;Xiao, Fuliang* ;Yang, Chang;Liu, Si;He, Yihua;...
期刊：
GEOPHYSICAL RESEARCH LETTERS ,2017年44(11):5251-5258 ISSN：0094-8276
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; Xiao, Fuliang; Zhou, Qinghua; Liu, Si; He, Yihua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Baker, D. N.] Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.;[Spence, H. E.] Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA.;[Reeves, G. D.] Los Alamos Natl Lab, Space Sci & Applicat Grp, Los Alamos, NM USA.;[Funsten, H. O.] Los Alamos Natl Lab, ISR Div, Los Alamos, NM USA.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.
关键词：
ECH waves;wave-particle interaction;RBSP results
摘要：
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≈ 5.7–5.8, 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, but the upper half during event B. The observed electron phase space density in both events is fitted by the subtracted bi-Maxwellian distribution, and the fitting functions are used to evaluate the local growth rates of ECH waves based on a linear theory for homogeneous plasmas. ECH waves are excited by the loss cone instability of 50 eV–1 keV electrons in the lower half of harmonic bands in the low-density plasmasphere in event A, and 1–10 keV electrons in the upper half of harmonic bands in a relatively high-density region in event B. The current results successfully explain observations and provide a first direct evidence on how ECH waves are generated in the lower and upper half of harmonic frequency bands.
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英文
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Explaining occurrences of auroral kilometric radiation in Van Allen radiation belts
作者：
Xiao, Fuliang* ;Zhou, Qinghua;Su, Zhenpeng;He, Zhaoguo;Yang, Chang;...
期刊：
GEOPHYSICAL RESEARCH LETTERS ,2016年43(23):11,971-11,978 ISSN：0094-8276
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; Xiao, Fuliang; Zhou, Qinghua; Liu, Si; He, Yihua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Su, Zhenpeng; Gao, Zhonglei] Univ Sci & Technol China, Chinese Acad Sci, Key Lab Basic Plasma Phys, Hefei, Peoples R China.;[He, Zhaoguo] Shenzhen Grad Sch, Harbin Inst Technol, Shenzhen, Peoples R China.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.
关键词：
AKR emissions;ray tracing simulations;radiation belts;geomagnetic storms;satellite data
摘要：
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's 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 small storm periods 4–6 April and 18–20 May 2013 and show, using a 3-D ray tracing simulation, that AKR can propagate downward all the way into the equatorial plane in the radiation belts under appropriate conditions. The simulated results can successfully explain the observed AKR's spatial distribution and frequency range, and the current results have a wide application to all other magnetized astrophysical objects in the universe. ©2016. American Geophysical Union. All Rights Reserved.
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英文
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Evolution of chorus emissions into plasmaspheric hiss observed by Van Allen Probes
作者：
Zhou, Qinghua;Xiao, Fuliang* ;Yang, Chang;Liu, Si;He, Yihua;...
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS ,2016年121(5):4518-4529 ISSN：2169-9380
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; Xiao, Fuliang; Zhou, Qinghua; Liu, Si; He, Yihua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Wygant, J. R.] Univ Minnesota, Sch Phys & Astron, Minneapolis, MN USA.;[Baker, D. N.] Univ Colorado Boulder, Lab Atmospher & Space Phys, Boulder, CO USA.;[Spence, H. E.] Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA.;[Reeves, G. D.] Los Alamos Natl Lab, Space Sci & Applicat Grp, Los Alamos, NM USA.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.
关键词：
plasmaspheric hiss;chorus waves;RBSP results
摘要：
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 observations form Van Allen Probes that chorus and hiss emissions occurred in the same range ∼300–1500 Hz with the peak wave power density about 10−5 nT2/Hz during a weak storm on 3 July 2014. Chorus emissions propagate in a broad region outside the plasmapause. Meanwhile, hiss emissions are confined inside the plasmasphere, with a higher intensity and a broader area at a lower frequency. A sum of bi-Maxwellian distribution is used to model the observed anisotropic electron distributions and to evaluate the instability of waves. A three-dimensional ray tracing simulation shows that a portion of chorus emission outside the plasmasphere can propagate into the plasmasphere and evolve into plasmaspheric hiss. Moreover, hiss waves below 1 kHz are more intense and propagate over a broader area than those above 1 kHz, consistent with the observation. The current results can explain distributions of the observed hiss emission and provide a further support for the mechanism of evolution of chorus into hiss emissions. ©2016. American Geophysical Union. All Rights Reserved.
语种：
英文
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Magnetospheric chorus wave instability induced by relativistic Kappa-type distributions
作者：
Yang QiWu;Yang Chang;He YiHua;Liu Si;Zhou QingHua;...
期刊：
中国科学:技术科学(英文版) ,2016年59(11):1739-1745 ISSN：1674-7321
通讯作者：
Xiao FuLiang
作者机构：
[Xiao FuLiang; Yang QiWu; Yang Chang; Liu Si; Zhou QingHua; He YiHua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Xiao FuLiang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha 410004, Hunan, Peoples R China.
关键词：
Kappa-type distribution;energetic electrons;wave-particle interaction;chorus wave instability
摘要：
We study the field-aligned propagating magnetospheric chorus wave instability using a fully relativistic wave growth formula, the previously developed relativistic Kappa-type (KT) distribution and the regular Kappa distribution of energetic electrons. We demonstrate that the peak growth rate using the nonrelativistic Kappa simulation is higher than that using either the relativistic KT or the Kappa simulation at/above 100 keV, because the significant relativistic effect yields a reduction in the relativistic anisotropy. The relativistic anisotropy A_(rel) basically decreases as the thermal parameter θ~2 increases, allowing the peak growth by relativistic KT or Kappa distribution to stay at the lower frequency region. The growth rates tend to increase with the loss-cone parameter l because the overall anisotropy increases. Moreover, at high energy ~1.0 MeV, both the growth rate and the upper cutoff frequency become smaller as l increases for the relativistic KT calculation because the significant relativistic effect reduces both the resonant anisotropy and the number of the hot electrons, which is in contrast to the relativistic and nonrelativistic Kappa distribution calculations because the less relativistic or non-relativistic effect enhances the resonant anisotropy as l increases. The above results can be applied to the whistler-mode wave instability in the outer radiation belts of the Earth, the Jovian inner magnetosphere and other astrophysical plasmas where relativistic electrons often exist.
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英文
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Wave-driven butterfly distribution of Van Allen belt relativistic electrons
作者：
Xiao, Fuliang* ;Yang, Chang;Su, Zhenpeng;Zhou, Qinghua;He, Zhaoguo;...
期刊：
Nature Communications ,2015年6(1):8590 ISSN：2041-1723
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; Xiao, Fuliang; Zhou, Qinghua; He, Yihua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha 410004, Hunan, Peoples R China.;[Su, Zhenpeng] Univ Sci & Technol China, Chinese Acad Sci, Key Lab Basic Plasma Phys, Hefei 230026, Anhui, Peoples R China.;[He, Zhaoguo] Chinese Acad Sci, Ctr Space Sci & Appl Res, Beijing 100190, Peoples R China.;[Baker, D. N.] Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA.;[Spence, H. E.] Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, 2nd Sect,South Wanjiali Rd 960, Changsha 410004, Hunan, Peoples R China.
关键词：
GLOBAL DISTRIBUTION;GEOMAGNETIC STORMS;MAGNETOSPHERE;RADIATION;CHORUS;ACCELERATION;PLASMASPHERE;PARTICLES;MODEL;IONS
摘要：
Van Allen radiation belts consist of relativistic electrons trapped by Earth's magnetic field. Trapped electrons often drift azimuthally around Earth and display a butterfly pitch angle distribution of a minimum at 90° further out than geostationary orbit. This is usually attributed to drift shell splitting resulting from day-night asymmetry in Eartha's magnetic field. However, direct observation of a butterfly distribution well inside of geostationary orbit and the origin of this phenomenon have not been provided so far. Here we report high-resolution observation that a unusual butterfly pitch angle distribution of relativistic electrons occurred within 5 Earth radii during the 28 June 2013 geomagnetic storm. Simulation results show that combined acceleration by chorus and magnetosonic waves can successfully explain the electron flux evolution both in the energy and butterfly pitch angle distribution. The current provides a great support for the mechanism of wave-driven butterfly distribution of relativistic electrons. © 2015 Macmillan Publishers Limited. All rights reserved.
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英文
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Penetration of magnetosonic waves into the plasmasphere observed by the Van Allen Probes
作者：
Xiao, Fuliang* ;Zhou, Qinghua;He, Yihua;Yang, Chang;Liu, Si;...
期刊：
GEOPHYSICAL RESEARCH LETTERS ,2015年42(18):7287-7294 ISSN：0094-8276
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; Xiao, Fuliang; Zhou, Qinghua; He, Yihua; Liu, Si] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Baker, D. N.] Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA.;[Spence, H. E.] Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA.;[Reeves, G. D.] Los Alamos Natl Lab, Space Sci & Applicat Grp, Los Alamos, NM USA.;[Funsten, H. O.] Los Alamos Natl Lab, ISR Div, Los Alamos, NM USA.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.
关键词：
Van Allen Probe results;magnetosonic waves;wave-particle interaction;proton ring distribution;radiation belts;geomagnetic storms
摘要：
During the small storm on 14-15 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 lower L shells outside the plasmasphere, with rapidly increasing path gains related to the continuous proton ring distribution. The waves then gradually cross the plasmapause into the deep plasmasphere, with almost unchanged path gains due to the falling proton ring distribution and higher ambient density. These results present the first report on how MS waves penetrate into the plasmasphere with the aid of the continuous proton ring distributions during weak geomagnetic activities. © 2015 American Geophysical Union. All Rights Reserved.
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英文
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Van Allen Probes observation and modeling of chorus excitation and propagation during weak geomagnetic activities
作者：
He, Yihua;Xiao, Fuliang* ;Zhou, Qinghua;Yang, Chang;Liu, Si;...
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS ,2015年120(8):6371-6385 ISSN：2169-9380
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; He, Yihua; Liu, Si; Xiao, Fuliang; Zhou, Qinghua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Baker, D. N.] Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA.;[Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.] Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.;[Spence, H. E.] Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA.;[Reeves, G. D.] Los Alamos Natl Lab, Space Sci & Applicat Grp, Los Alamos, NM USA.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.
关键词：
chorus wave excitation;energetic electrons;wave-particle interaction;Van Allen probes results;geomagnetic storm
摘要：
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 bi-Maxwellian distribution to model the observed electron distribution, we perform ray tracing simulations to show that nightside chorus waves are indeed produced by the observed electron distribution with a peak growth for a field-aligned propagation approximately between 0.3fce and 0.4fce, at latitude <7°. Moreover, chorus waves launched with initial normal angles either θ<90° or >90° propagate along the field either northward or southward and then bounce back either away from Earth for a lower frequency or toward Earth for higher frequencies. The current results indicate that nightside chorus waves can be excited even during weak geomagnetic activities in cases of continuous injection associated with negative Bz. Moreover, we examine a dayside event during a small storm C on 8 May 2014 (Dst≈−45) and find that the observed anisotropic energetic electron distributions potentially contribute to the generation of dayside chorus waves, but this requires more thorough studies in the future.
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英文
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Influence of wave normal angles on hiss-electron interaction in Earth's slot region
作者：
Gao, Yuzhu;Xiao, Fuliang* ;Yan, Qi;Yang, Chang;Liu, Si;...
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS ,2015年120(11):9385-9400 ISSN：2169-9380
通讯作者：
Xiao, Fuliang
作者机构：
[Yan, Qi; Yang, Chang; Xiao, Fuliang; Liu, Si; He, Yihua; Zhou, Qinghua; Gao, Yuzhu] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Peoples R China.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Peoples R China.
关键词：
energetic electrons;plasmaspheric hiss;the slot region;wave normal angle;wave-particle interaction
摘要：
Wave-particle interaction which occurs in the radiation belts is generally determined by variations in wave normal angles. Using the Gaussian wave normal angle (X = tan theta) distribution, we study the influence of peak wave normal angle (X-m= tan theta(m)) on gyroresonance between plasmaspheric hiss waves and energetic electrons in the slot regions L = 2.5, 3.0, and 3.5. The bounce-averaged diffusion coefficients are calculated for different X-m = 0, 1, 3, 5, and then the phase space density (PSD) evolutions of energetic electrons driven by hiss waves are simulated over a continuous energy range 0.2-5 MeV. As X-m increases, diffusion coefficients basically decrease mainly from the medium to a critical pitch angle alpha(c) for E-k <= 1.0 MeV but increase at lower pitch angles for E-k > 1.0 MeV. Differences of diffusion coefficients between X-m = 0 and 1 are close but become substantial as X-m >= 3. Hiss can cause substantial drops in electron PSDs for E-k <= 0.5 MeV and X-m <= 1 from the loss cone alpha(L) to alpha(c). For E-k >= 1.0 MeV, such PSD drops become much smaller and confined in the lower pitch angles close to alpha(L) for each X-m. In contrast, electron PSD increases for E-k <= 1.0 MeV above alpha(c) at L = 2.5 and 3.0, probably because momentum diffusion coefficients increase steeply above alpha(c). The current results demonstrate that gyroresonance between plasmaspheric hiss and energetic electrons in the slot region is strongly associated with variations of peak wave normal angles, which should be integrated into future global modeling of radiation belt dynamics.
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英文
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Van Allen Probes observations linking radiation belt electrons to chorus waves during 2014 multiple storms
作者：
Liu, Si;Xiao, Fuliang* ;Yang, Chang;He, Yihua;Zhou, Qinghua;...
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS ,2015年120(2):938-948 ISSN：2169-9380
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; Liu, Si; He, Yihua; Xiao, Fuliang; Zhou, Qinghua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.] Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.;[Spence, H. E.] Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA.;[Reeves, G. D.] Los Alamos Natl Lab, Space Sci & Applicat Grp, Los Alamos, NM USA.;[Funsten, H. O.] Los Alamos Natl Lab, ISR Div, Los Alamos, NM USA.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.
关键词：
RBSP results;chorus and hiss excitation;relativistic electron acceleration;energetic electron flux;wave-particle interaction
摘要：
During 18 February to 2 March 2014, the Van Allen Probes encountered multiple geomagnetic storms and simultaneously observed intensified chorus and hiss waves. During this period, there were substantial enhancements in fluxes of energetic (53.8–108.3 keV) and relativistic (2–3.6 MeV) electrons. Chorus waves were excited at locations L = 4–6.2 after the fluxes of energetic were greatly enhanced, with a lower frequency band and wave amplitudes ∼20–100 pT. Strong hiss waves occurred primarily in the main phases or below the location L = 4 in the recovery phases. Relativistic electron fluxes decreased in the main phases due to the adiabatic (e.g., the magnetopause shadowing) or nonadiabatic (hiss-induced scattering) processes. In the recovery phases, relativistic electron fluxes either increased in the presence of enhanced chorus or remained unchanged in the absence of strong chorus or hiss. The observed relativistic electron phase space density peaked around L∗ = 4.5, characteristic of local acceleration. This multiple-storm period reveals a typical picture that chorus waves are excited by the energetic electrons at first and then produce efficient acceleration of relativistic electrons. This further demonstrates that the interplay between both competing mechanisms of chorus-driven acceleration and hiss-driven scattering often occurs in the outer radiation belts.
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英文
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Chorus acceleration of radiation belt relativistic electrons during March 2013 geomagnetic storm
作者：
Xiao, Fuliang* ;Yang, Chang;He, Zhaoguo;Su, Zhenpeng;Zhou, Qinghua;...
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS ,2014年119(5):3325-3332 ISSN：2169-9380
通讯作者：
Xiao, Fuliang
作者机构：
[Yang, Chang; He, Yihua; Xiao, Fuliang; Zhou, Qinghua] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.;[He, Zhaoguo] Chinese Acad Sci, Ctr Space Sci & Appl Res, Beijing, Peoples R China.;[Su, Zhenpeng] Univ Sci & Technol China, Dept Geophys & Planetary Sci, CAS Key Lab Geospace Environm, Hefei 230026, Peoples R China.;[Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.] Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.;[Spence, H. E.] Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA.
通讯机构：
[Xiao, Fuliang] C;Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha, Hunan, Peoples R China.
关键词：
chorus waves;wave-particle interaction;relativistic electron acceleration;RBSP results
摘要：
The recent launching of Van Allen probes provides an unprecedent opportunity to investigate variations of the radiation belt relativistic electrons. During the 17-19 March 2013 storm, the Van Allen probes simultaneously detected strong chorus waves and substantial increases in fluxes of relativistic (2 - 4.5 MeV) electrons around L = 4.5. Chorus waves occurred within the lower band 0.1-0.5fce (the electron equatorial gyrofrequency), with a peak spectral density ∼10-4 nT 2/Hz. Correspondingly, relativistic electron fluxes increased by a factor of 102-103 during the recovery phase compared to the main phase levels. By means of a Gaussian fit to the observed chorus spectra, the drift and bounce-averaged diffusion coefficients are calculated and then used to solve a 2-D Fokker-Planck diffusion equation. Numerical simulations demonstrate that the lower-band chorus waves indeed produce such huge enhancements in relativistic electron fluxes within 15 h, fitting well with the observation. Key Points Initial RBSP correlated data of chorus waves and relativistic electron fluxes A realistic simulation to examine effect of chorus on relativistic electron flux Chorus yields huge increases in electron flux rapidly, consistent with data ©2014. American Geophysical Union. All Rights Reserved.
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