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Acceleration
Authors: Su Zhenpeng, Xiao Fuliang, Zheng Huinan, and Zhu Hui
Title: Chorus-driven acceleration of radiation belt electrons in the unusual temporal/spatial regions
Abstract: Cyclotron resonance with whistler-mode chorus waves is an important mechanism for the local acceleration of radiation belt energetic electrons. Such acceleration process has been widely investigated during the storm times, and its favored region is usually considered to be the low-density plasmatrough with magnetic local time (MLT) from midnight through dawn to noon. Here we present two case studies on the chorus-driven acceleration of radiation belt electrons in some “unusual” temporal /spatial regions. (1) The first event recorded by the Van Allen Probes during the nonstorm times from 21 to 23 February 2013. Within two days, a new radiation belt centering around L=5.8 formed and gradually merged with the original outer belt. The corresponding relativistic electron fluxes increased by. . .
Date: 08/2014 Publisher: IEEE DOI: 10.1109/URSIGASS.2014.6929875 Available at: http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=6929875
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AKR emissions
Authors: Xiao Fuliang, Zhou Qinghua, Su Zhenpeng, He Zhaoguo, Yang Chang, et al.
Title: Explaining occurrences of auroral kilometric radiation in Van Allen radiation belts
Abstract: 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. . .
Date: 12/2016 Publisher: Geophysical Research Letters Pages: 11,971 - 11,978 DOI: 10.1002/2016GL071728 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071728/full
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aurora
Authors: Gao Zhonglei, Su Zhenpeng, Xiao Fuliang, Summers Danny, Liu Nigang, et al.
Title: Nonlinear coupling between whistler-mode chorus and electron cyclotron harmonic waves in the magnetosphere
Abstract: Electromagnetic whistler‐mode chorus and electrostatic electron cyclotron harmonic (ECH) waves can contribute significantly to auroral electron precipitation and radiation belt electron acceleration. In the past, linear and nonlinear wave‐particle interactions have been proposed to explain the occurrences of these magnetospheric waves. By analyzing Van Allen Probes data, we present here the first evidence for nonlinear coupling between chorus and ECH waves. The sum‐frequency and difference‐frequency interactions produced the ECH sidebands with discrete frequency sweeping structures exactly corresponding to the chorus rising tones. The newly‐generated weak sidebands did not satisfy the original electrostatic wave dispersion relation. After the generation of chorus and normal ECH w. . .
Date: 11/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080635 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080635
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Auroral kilometric radiation
Authors: Zhao Wanli, Liu Si, Zhang Sai, Zhou Qinghua, Yang Chang, et al.
Title: Global Occurrences of Auroral Kilometric Radiation Related to Suprathermal Electrons in Radiation Belts
Abstract: 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 th. . .
Date: 07/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL083944 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL083944
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butterfly distribution relativistic electrons radiation belts wave-particle interaction dayside chorus
Authors: Jin YuYue, Yang Chang, He Yihua, Liu Si, Zhou Qinghua, et al.
Title: Butterfly distribution of Earth’s radiation belt relativistic electrons induced by dayside chorus
Abstract: Previous theoretical studies have shown that dayside chorus can produce butterfly distribution of energetic electrons in the Earth’s radiation belts by preferentially accelerating medium pitch angle electrons, but this requires the further confirmation from high-resolution satellite observation. Here, we report correlated Van Allen Probes data on wave and particle during the 11–13 April, 2014 geomagnetic storm. We find that a butterfly pitch angle distribution of relativistic electrons is formed around the location L = 4.52, corresponding to the presence of enhanced dayside chorus. Using a Gaussian distribution fit to the observed chorus spectra, we calculate the bounce-averaged diffusion rates and solve two-dimensional Fokker-Planck equation. Numerical results demonstrate that acceler. . .
Date: 09/2017 Publisher: Science China Technological Sciences DOI: 10.1007/s11431-017-9067-y Available at: https://link.springer.com/article/10.1007/s11431-017-9067-y
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butterfly distributions
Authors: Yang Chang, Su Zhenpeng, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: A positive correlation between energetic electron butterfly distributions and magnetosonic waves in the radiation belt slot region
Abstract: Energetic (hundreds of keV) electrons in the radiation belt slot region have been found to exhibit the butterfly pitch angle distributions. Resonant interactions with magnetosonic and whistler-mode waves are two potential mechanisms for the formation of these peculiar distributions. Here we perform a statistical study of energetic electron pitch angle distribution characteristics measured by Van Allen Probes in the slot region during a three-year period from May 2013 to May 2016. Our results show that electron butterfly distributions are closely related to magnetosonic waves rather than to whistler-mode waves. Both electron butterfly distributions and magnetosonic waves occur more frequently at the geomagnetically active times than at the quiet times. In a statistical sense, more distinct . . .
Date: 03/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073116 Available at: http://doi.wiley.com/10.1002/2017GL073116
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Chorus wave
Authors: Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Quantifying the relative contributions of substorm injections and chorus waves to the rapid outward extension of electron radiation belt
Abstract: We study the rapid outward extension of the electron radiation belt on a timescale of several hours during three events observed by RBSP and THEMIS satellites, and particularly quantify the contributions of substorm injections and chorus waves to the electron flux enhancement near the outer boundary of radiation belt. A comprehensive analysis including both observations and simulations is performed for the first event on 26 May 2013. The outer boundary of electron radiation belt moved from L = 5.5 to L > 6.07 over about 6 hours, with up to four orders of magnitude enhancement in the 30 keV-5 MeV electron fluxes at L = 6. The observations show that the substorm injection can cause 100% and 20% of the total subrelativistic (~0.1 MeV) and relativistic (2-5 MeV) electron . . .
Date: 12/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020709 Available at: http://doi.wiley.com/10.1002/2014JA020709
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Authors: Gao Zhonglei, Su Zhenpeng, Xiao Fuliang, Summers Danny, Liu Nigang, et al.
Title: Nonlinear coupling between whistler-mode chorus and electron cyclotron harmonic waves in the magnetosphere
Abstract: Electromagnetic whistler‐mode chorus and electrostatic electron cyclotron harmonic (ECH) waves can contribute significantly to auroral electron precipitation and radiation belt electron acceleration. In the past, linear and nonlinear wave‐particle interactions have been proposed to explain the occurrences of these magnetospheric waves. By analyzing Van Allen Probes data, we present here the first evidence for nonlinear coupling between chorus and ECH waves. The sum‐frequency and difference‐frequency interactions produced the ECH sidebands with discrete frequency sweeping structures exactly corresponding to the chorus rising tones. The newly‐generated weak sidebands did not satisfy the original electrostatic wave dispersion relation. After the generation of chorus and normal ECH w. . .
Date: 11/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080635 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080635
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chorus wave excitation
Authors: He Yihua, Xiao Fuliang, Zhou Qinghua, Yang Chang, Liu Si, et al.
Title: Van Allen Probes observation and modeling of chorus excitation and propagation during weak geomagnetic activities
Abstract: 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 around bet. . .
Date: 07/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021376 Available at: http://doi.wiley.com/10.1002/2015JA021376
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chorus waves
Authors: Zhou Qinghua, Xiao Fuliang, Yang Chang, Liu Si, He Yihua, et al.
Title: Evolution of chorus emissions into plasmaspheric hiss observed by Van Allen Probes
Abstract: 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. Meanwhi. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: 4518 - 4529 DOI: 10.1002/2016JA022366 Available at: http://doi.wiley.com/10.1002/2016JA022366
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chorus-driven acceleration
Authors: Liu Si, Yan Qi, Yang Chang, Zhou Qinghua, He Zhaoguo, et al.
Title: Quantifying Extremely Rapid Flux Enhancements of Radiation Belt Relativistic Electrons Associated With Radial Diffusion
Abstract: 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 2 h) flux enhancements of relativistic (1.8–3.4 MeV) 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 (∼100–300 keV) 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 phas. . .
Date: 02/2018 Publisher: Geophysical Research Letters Pages: 1262 - 1270 DOI: 10.1002/grl.v45.310.1002/2017GL076513 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL076513/full
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Cyclotron instability
Authors: Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Disappearance of plasmaspheric hiss following interplanetary shock
Abstract: Plasmaspheric hiss is one of the important plasma waves controlling radiation belt dynamics. Its spatiotemporal distribution and generation mechanism are presently the object of active research. We here give the first report on the shock-induced disappearance of plasmaspheric hiss observed by the Van Allen Probes on 8 October 2013. This special event exhibits the dramatic variability of plasmaspheric hiss and provides a good opportunity to test its generation mechanisms. The origination of plasmaspheric hiss from plasmatrough chorus is suggested to be an appropriate prerequisite to explain this event. The shock increased the suprathermal electron fluxes, and then the enhanced Landau damping promptly prevented chorus waves from entering the plasmasphere. Subsequently, the shrinking magnetop. . .
Date: 03/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL063906 Available at: http://doi.wiley.com/10.1002/2015GL063906
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Cyclotron resonance
Authors: Gao Zhonglei, Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, et al.
Title: Intense low-frequency chorus waves observed by Van Allen Probes: Fine structures and potential effect on radiation belt electrons
Abstract: Frequency distribution is a vital factor in determining the contribution of whistler-mode chorus to radiation belt electron dynamics. Chorus is usually considered to occur in the frequency range 0.1–0.8 inline image (with the equatorial electron gyrofrequency inline image). We here report an event of intense low-frequency chorus with nearly half of wave power distributed below 0.1 inline image observed by Van Allen Probe A on 27 August 2014. This emission propagated quasi-parallel to the magnetic field and exhibited hiss-like signatures most of the time. The low-frequency chorus can produce the rapid loss of low-energy (∼0.1 MeV) electrons, different from the normal chorus. For high-energy (≥0.5 MeV) electrons, the low-frequency chorus can yield comparable momentum diffusion to tha. . .
Date: 02/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL067687 Available at: http://doi.wiley.com/10.1002/2016GL067687
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Authors: Zhu Hui, Su Zhenpeng, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Plasmatrough exohiss waves observed by Van Allen Probes: Evidence for leakage from plasmasphere and resonant scattering of radiation belt electrons
Abstract: Exohiss waves are whistler mode hiss observed in the plasmatrough region. We present a case study of exohiss waves and the corresponding background plasma distributions observed by the Van Allen Probes in the dayside low-latitude region. The analysis of wave Poynting fluxes, suprathermal electron fluxes and cold electron densities supports the scenario that exohiss leaks from the plasmasphere into the plasmatrough. Quasilinear calculations further reveal that exohiss can potentially cause the resonant scattering loss of radiation belt electrons ~Date: 02/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062964 Available at: http://doi.wiley.com/10.1002/2014GL062964
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Authors: Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Disappearance of plasmaspheric hiss following interplanetary shock
Abstract: Plasmaspheric hiss is one of the important plasma waves controlling radiation belt dynamics. Its spatiotemporal distribution and generation mechanism are presently the object of active research. We here give the first report on the shock-induced disappearance of plasmaspheric hiss observed by the Van Allen Probes on 8 October 2013. This special event exhibits the dramatic variability of plasmaspheric hiss and provides a good opportunity to test its generation mechanisms. The origination of plasmaspheric hiss from plasmatrough chorus is suggested to be an appropriate prerequisite to explain this event. The shock increased the suprathermal electron fluxes, and then the enhanced Landau damping promptly prevented chorus waves from entering the plasmasphere. Subsequently, the shrinking magnetop. . .
Date: 03/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL063906 Available at: http://doi.wiley.com/10.1002/2015GL063906
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Dayside chorus generation
Authors: He Yihua, Xiao Fuliang, Su Zhenpeng, Zheng Huinan, Yang Chang, et al.
Title: Generation of lower L -shell dayside chorus by energetic electrons from the plasmasheet
Abstract: Currently, the generation mechanism for the lower L‐shell dayside chorus has still remained an open question. Here, we report two storm events: 06‐07 March 2016 and 20‐21 January 2016, when Van Allen Probes observed enhanced dayside chorus with lower and higher wave normal angles (the angles between the wave vector and the geomagnetic field) in the region of L = 3.5‐6.3 and MLT = 5.6‐13.5. Hot and energetic (∼ 1‐100 keV) electrons displayed enhancements in fluxes and anisotropy when they were injected from the plasmasheet 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 ma. . .
Date: 09/2018 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1029/2017JA024889 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2017JA024889
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ECH waves
Authors: Zhou Qinghua, Xiao Fuliang, Yang Chang, Liu Si, He Yihua, et al.
Title: Generation of lower and upper bands of electrostatic electron cyclotron harmonic waves in the Van Allen radiation belts
Abstract: 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.. . .
Date: 05/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073051 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL073051/full
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Electron acceleration
Authors: Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Quantifying the relative contributions of substorm injections and chorus waves to the rapid outward extension of electron radiation belt
Abstract: We study the rapid outward extension of the electron radiation belt on a timescale of several hours during three events observed by RBSP and THEMIS satellites, and particularly quantify the contributions of substorm injections and chorus waves to the electron flux enhancement near the outer boundary of radiation belt. A comprehensive analysis including both observations and simulations is performed for the first event on 26 May 2013. The outer boundary of electron radiation belt moved from L = 5.5 to L > 6.07 over about 6 hours, with up to four orders of magnitude enhancement in the 30 keV-5 MeV electron fluxes at L = 6. The observations show that the substorm injection can cause 100% and 20% of the total subrelativistic (~0.1 MeV) and relativistic (2-5 MeV) electron . . .
Date: 12/2014 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2014JA020709 Available at: http://doi.wiley.com/10.1002/2014JA020709
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Authors: Yang Chang, Su Zhenpeng, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: A positive correlation between energetic electron butterfly distributions and magnetosonic waves in the radiation belt slot region
Abstract: Energetic (hundreds of keV) electrons in the radiation belt slot region have been found to exhibit the butterfly pitch angle distributions. Resonant interactions with magnetosonic and whistler-mode waves are two potential mechanisms for the formation of these peculiar distributions. Here we perform a statistical study of energetic electron pitch angle distribution characteristics measured by Van Allen Probes in the slot region during a three-year period from May 2013 to May 2016. Our results show that electron butterfly distributions are closely related to magnetosonic waves rather than to whistler-mode waves. Both electron butterfly distributions and magnetosonic waves occur more frequently at the geomagnetically active times than at the quiet times. In a statistical sense, more distinct . . .
Date: 03/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073116 Available at: http://doi.wiley.com/10.1002/2017GL073116
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electron cyclotron harmonic wave
Authors: Gao Zhonglei, Su Zhenpeng, Xiao Fuliang, Summers Danny, Liu Nigang, et al.
Title: Nonlinear coupling between whistler-mode chorus and electron cyclotron harmonic waves in the magnetosphere
Abstract: Electromagnetic whistler‐mode chorus and electrostatic electron cyclotron harmonic (ECH) waves can contribute significantly to auroral electron precipitation and radiation belt electron acceleration. In the past, linear and nonlinear wave‐particle interactions have been proposed to explain the occurrences of these magnetospheric waves. By analyzing Van Allen Probes data, we present here the first evidence for nonlinear coupling between chorus and ECH waves. The sum‐frequency and difference‐frequency interactions produced the ECH sidebands with discrete frequency sweeping structures exactly corresponding to the chorus rising tones. The newly‐generated weak sidebands did not satisfy the original electrostatic wave dispersion relation. After the generation of chorus and normal ECH w. . .
Date: 11/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080635 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080635
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electron ring distribution
Authors: Chen Yaru, Zhou Qinghua, He Yihua, Yang Chang, Liu Si, et al.
Title: Global occurrences of electrostatic electron cyclotron harmonic waves associated with radiation belt electron distributions
Abstract: Electrostatic electron cyclotron harmonic (ECH) waves can yield diffuse aurora primarily at higher L‐shells by driving efficient precipitation loss of plasma sheet electrons. Here using the Van Allen Probes high resolution data, we examine in detail the global occurrences of ECH waves during the period from October 1, 2012 to June 30, 2017 and find that there are totally 419 events of enhanced ECH waves. The statistical results demonstrate that ECH waves can be present over a broad region of L=4‐6 and 00‐24 MLT, with a 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 keV. Both ECH wave events and the electron ring distributions are closely related and . . .
Date: 04/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL082668 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082668
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ELF chorus waves
Authors: Xiao Fuliang, Liu Si, Tao Xin, Su Zhenpeng, Zhou Qinghua, et al.
Title: Generation of extremely low frequency chorus in Van Allen radiation belts
Abstract: 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 p. . .
Date: 03/2017 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2016JA023561 Available at: http://doi.wiley.com/10.1002/2016JA023561
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energetic electron
Authors: Yang Chang, Xiao Fuliang, He Yihua, Liu Si, Zhou Qinghua, et al.
Title: Storm-time evolution of outer radiation belt relativistic electrons by a nearly continuous distribution of chorus
Abstract: During the 13-14 November 2012 storm, Van Allen Probe A simultaneously observed a 10-h period of enhanced chorus (including quasi-parallel and oblique propagation components) and relativistic electron fluxes over a broad range of L = 3−6 and MLT=2 − 10 within a complete orbit cycle. By adopting a Gaussian fit to the observed wave spectra, we obtain the wave parameters and calculate the bounce-averaged diffusion coefficients. We solve the Fokker-Planck diffusion equation to simulate flux evolutions of relativistic (1.8-4.2 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∘. . .
Date: 02/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL075894 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL075894/full
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energetic electrons
Authors: He Yihua, Xiao Fuliang, Zhou Qinghua, Yang Chang, Liu Si, et al.
Title: Van Allen Probes observation and modeling of chorus excitation and propagation during weak geomagnetic activities
Abstract: 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 around bet. . .
Date: 07/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021376 Available at: http://doi.wiley.com/10.1002/2015JA021376
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Exohiss
Authors: Zhu Hui, Su Zhenpeng, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Plasmatrough exohiss waves observed by Van Allen Probes: Evidence for leakage from plasmasphere and resonant scattering of radiation belt electrons
Abstract: Exohiss waves are whistler mode hiss observed in the plasmatrough region. We present a case study of exohiss waves and the corresponding background plasma distributions observed by the Van Allen Probes in the dayside low-latitude region. The analysis of wave Poynting fluxes, suprathermal electron fluxes and cold electron densities supports the scenario that exohiss leaks from the plasmasphere into the plasmatrough. Quasilinear calculations further reveal that exohiss can potentially cause the resonant scattering loss of radiation belt electrons ~Date: 02/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062964 Available at: http://doi.wiley.com/10.1002/2014GL062964
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Geomagnetic storm
Authors: Yang Chang, Xiao Fuliang, He Yihua, Liu Si, Zhou Qinghua, et al.
Title: Storm-time evolution of outer radiation belt relativistic electrons by a nearly continuous distribution of chorus
Abstract: During the 13-14 November 2012 storm, Van Allen Probe A simultaneously observed a 10-h period of enhanced chorus (including quasi-parallel and oblique propagation components) and relativistic electron fluxes over a broad range of L = 3−6 and MLT=2 − 10 within a complete orbit cycle. By adopting a Gaussian fit to the observed wave spectra, we obtain the wave parameters and calculate the bounce-averaged diffusion coefficients. We solve the Fokker-Planck diffusion equation to simulate flux evolutions of relativistic (1.8-4.2 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∘. . .
Date: 02/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL075894 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL075894/full
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Authors: He Yihua, Xiao Fuliang, Zhou Qinghua, Yang Chang, Liu Si, et al.
Title: Van Allen Probes observation and modeling of chorus excitation and propagation during weak geomagnetic activities
Abstract: 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 around bet. . .
Date: 07/2015 Publisher: Journal of Geophysical Research: Space Physics DOI: 10.1002/2015JA021376 Available at: http://doi.wiley.com/10.1002/2015JA021376
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Geomagnetic storms
Authors: Xiao Fuliang, Zhou Qinghua, He Yihua, Yang Chang, Liu Si, et al.
Title: Penetration of magnetosonic waves into the plasmasphere observed by the Van Allen Probes
Abstract: 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 an. . .
Date: 09/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL065745 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015GL065745/full
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Authors: Xiao Fuliang, Zhou Qinghua, Su Zhenpeng, He Zhaoguo, Yang Chang, et al.
Title: Explaining occurrences of auroral kilometric radiation in Van Allen radiation belts
Abstract: 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. . .
Date: 12/2016 Publisher: Geophysical Research Letters Pages: 11,971 - 11,978 DOI: 10.1002/2016GL071728 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2016GL071728/full
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global occurrence
Authors: Zhao Wanli, Liu Si, Zhang Sai, Zhou Qinghua, Yang Chang, et al.
Title: Global Occurrences of Auroral Kilometric Radiation Related to Suprathermal Electrons in Radiation Belts
Abstract: 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 th. . .
Date: 07/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL083944 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL083944
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global occurrences
Authors: Chen Yaru, Zhou Qinghua, He Yihua, Yang Chang, Liu Si, et al.
Title: Global occurrences of electrostatic electron cyclotron harmonic waves associated with radiation belt electron distributions
Abstract: Electrostatic electron cyclotron harmonic (ECH) waves can yield diffuse aurora primarily at higher L‐shells by driving efficient precipitation loss of plasma sheet electrons. Here using the Van Allen Probes high resolution data, we examine in detail the global occurrences of ECH waves during the period from October 1, 2012 to June 30, 2017 and find that there are totally 419 events of enhanced ECH waves. The statistical results demonstrate that ECH waves can be present over a broad region of L=4‐6 and 00‐24 MLT, with a 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 keV. Both ECH wave events and the electron ring distributions are closely related and . . .
Date: 04/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL082668 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082668
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Hiss-like band
Authors: Gao Zhonglei, Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, et al.
Title: Intense low-frequency chorus waves observed by Van Allen Probes: Fine structures and potential effect on radiation belt electrons
Abstract: Frequency distribution is a vital factor in determining the contribution of whistler-mode chorus to radiation belt electron dynamics. Chorus is usually considered to occur in the frequency range 0.1–0.8 inline image (with the equatorial electron gyrofrequency inline image). We here report an event of intense low-frequency chorus with nearly half of wave power distributed below 0.1 inline image observed by Van Allen Probe A on 27 August 2014. This emission propagated quasi-parallel to the magnetic field and exhibited hiss-like signatures most of the time. The low-frequency chorus can produce the rapid loss of low-energy (∼0.1 MeV) electrons, different from the normal chorus. For high-energy (≥0.5 MeV) electrons, the low-frequency chorus can yield comparable momentum diffusion to tha. . .
Date: 02/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL067687 Available at: http://doi.wiley.com/10.1002/2016GL067687
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interplanetary shock
Authors: Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Disappearance of plasmaspheric hiss following interplanetary shock
Abstract: Plasmaspheric hiss is one of the important plasma waves controlling radiation belt dynamics. Its spatiotemporal distribution and generation mechanism are presently the object of active research. We here give the first report on the shock-induced disappearance of plasmaspheric hiss observed by the Van Allen Probes on 8 October 2013. This special event exhibits the dramatic variability of plasmaspheric hiss and provides a good opportunity to test its generation mechanisms. The origination of plasmaspheric hiss from plasmatrough chorus is suggested to be an appropriate prerequisite to explain this event. The shock increased the suprathermal electron fluxes, and then the enhanced Landau damping promptly prevented chorus waves from entering the plasmasphere. Subsequently, the shrinking magnetop. . .
Date: 03/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL063906 Available at: http://doi.wiley.com/10.1002/2015GL063906
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Landau damping
Authors: Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Disappearance of plasmaspheric hiss following interplanetary shock
Abstract: Plasmaspheric hiss is one of the important plasma waves controlling radiation belt dynamics. Its spatiotemporal distribution and generation mechanism are presently the object of active research. We here give the first report on the shock-induced disappearance of plasmaspheric hiss observed by the Van Allen Probes on 8 October 2013. This special event exhibits the dramatic variability of plasmaspheric hiss and provides a good opportunity to test its generation mechanisms. The origination of plasmaspheric hiss from plasmatrough chorus is suggested to be an appropriate prerequisite to explain this event. The shock increased the suprathermal electron fluxes, and then the enhanced Landau damping promptly prevented chorus waves from entering the plasmasphere. Subsequently, the shrinking magnetop. . .
Date: 03/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL063906 Available at: http://doi.wiley.com/10.1002/2015GL063906
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Authors: Zhu Hui, Su Zhenpeng, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Plasmatrough exohiss waves observed by Van Allen Probes: Evidence for leakage from plasmasphere and resonant scattering of radiation belt electrons
Abstract: Exohiss waves are whistler mode hiss observed in the plasmatrough region. We present a case study of exohiss waves and the corresponding background plasma distributions observed by the Van Allen Probes in the dayside low-latitude region. The analysis of wave Poynting fluxes, suprathermal electron fluxes and cold electron densities supports the scenario that exohiss leaks from the plasmasphere into the plasmatrough. Quasilinear calculations further reveal that exohiss can potentially cause the resonant scattering loss of radiation belt electrons ~Date: 02/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062964 Available at: http://doi.wiley.com/10.1002/2014GL062964
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Landau resonance
Authors: Yang Chang, Su Zhenpeng, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: A positive correlation between energetic electron butterfly distributions and magnetosonic waves in the radiation belt slot region
Abstract: Energetic (hundreds of keV) electrons in the radiation belt slot region have been found to exhibit the butterfly pitch angle distributions. Resonant interactions with magnetosonic and whistler-mode waves are two potential mechanisms for the formation of these peculiar distributions. Here we perform a statistical study of energetic electron pitch angle distribution characteristics measured by Van Allen Probes in the slot region during a three-year period from May 2013 to May 2016. Our results show that electron butterfly distributions are closely related to magnetosonic waves rather than to whistler-mode waves. Both electron butterfly distributions and magnetosonic waves occur more frequently at the geomagnetically active times than at the quiet times. In a statistical sense, more distinct . . .
Date: 03/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073116 Available at: http://doi.wiley.com/10.1002/2017GL073116
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Local Acceleration due to Wave-Particle Interaction
Authors: Summers D., Thorne Richard M, and Xiao Fuliang
Title: Relativistic theory of wave-particle resonant diffusion with application to electron acceleration in the magnetosphere
Abstract: Resonant diffusion curves for electron cyclotron resonance with field-aligned electromagnetic R mode and L mode electromagnetic ion cyclotron (EMIC) waves are constructed using a fully relativistic treatment. Analytical solutions are derived for the case of a single-ion plasma, and a numerical scheme is developed for the more realistic case of a multi-ion plasma. Diffusion curves are presented, for plasma parameters representative of the Earth's magnetosphere at locations both inside and outside the plasmapause. The results obtained indicate minimal electron energy change along the diffusion curves for resonant interaction with L mode waves. Intense storm time EMIC waves are therefore ineffective for electron stochastic acceleration, although these waves could induce rapid pitch angle scat. . .
Date: 09/1998 Publisher: Journal of Geophysical Research Pages: 20487 - 20500 DOI: 10.1029/98JA01740 Available at: http://onlinelibrary.wiley.com/doi/10.1029/98JA01740/abstract
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Low-frequency chorus
Authors: Gao Zhonglei, Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, et al.
Title: Intense low-frequency chorus waves observed by Van Allen Probes: Fine structures and potential effect on radiation belt electrons
Abstract: Frequency distribution is a vital factor in determining the contribution of whistler-mode chorus to radiation belt electron dynamics. Chorus is usually considered to occur in the frequency range 0.1–0.8 inline image (with the equatorial electron gyrofrequency inline image). We here report an event of intense low-frequency chorus with nearly half of wave power distributed below 0.1 inline image observed by Van Allen Probe A on 27 August 2014. This emission propagated quasi-parallel to the magnetic field and exhibited hiss-like signatures most of the time. The low-frequency chorus can produce the rapid loss of low-energy (∼0.1 MeV) electrons, different from the normal chorus. For high-energy (≥0.5 MeV) electrons, the low-frequency chorus can yield comparable momentum diffusion to tha. . .
Date: 02/2016 Publisher: Geophysical Research Letters DOI: 10.1002/2016GL067687 Available at: http://doi.wiley.com/10.1002/2016GL067687
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magnetosonic wave
Authors: Yang Chang, Su Zhenpeng, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: A positive correlation between energetic electron butterfly distributions and magnetosonic waves in the radiation belt slot region
Abstract: Energetic (hundreds of keV) electrons in the radiation belt slot region have been found to exhibit the butterfly pitch angle distributions. Resonant interactions with magnetosonic and whistler-mode waves are two potential mechanisms for the formation of these peculiar distributions. Here we perform a statistical study of energetic electron pitch angle distribution characteristics measured by Van Allen Probes in the slot region during a three-year period from May 2013 to May 2016. Our results show that electron butterfly distributions are closely related to magnetosonic waves rather than to whistler-mode waves. Both electron butterfly distributions and magnetosonic waves occur more frequently at the geomagnetically active times than at the quiet times. In a statistical sense, more distinct . . .
Date: 03/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073116 Available at: http://doi.wiley.com/10.1002/2017GL073116
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Authors: Zhou Qinghua, Xiao Fuliang, Yang Chang, Liu Si, Kletzing C A, et al.
Title: Excitation of nightside magnetosonic waves observed by Van Allen Probes
Abstract: During the recovery phase of the geomagnetic storm on 30-31 March 2013, Van Allen Probe A detected enhanced magnetosonic (MS) waves in a broad range of L =1.8-4.7 and MLT =17-22 h, with a frequency range ~10-100 Hz. In the meanwhile, distinct proton ring distributions with peaks at energies of ~10 keV, were also observed in L =3.2-4.6 and L =5.0-5.6. Using a subtracted bi-Maxwellian distribution to model the observed proton ring distribution, we perform three dimensional ray tracing to investigate the instability, propagation and spatial distribution of MS waves. Numerical results show that nightside MS waves are produced by proton ring distribution and grow rapidly from the source location L =5.6 to the location L =5.0, but remain nearly stable at locations L <5.0 Moreover, waves launched. . .
Date: 11/2014 Publisher: Journal of Geophysical Research: Space Physics Pages: n/a - n/a DOI: 10.1002/2014JA020481 Available at: http://doi.wiley.com/10.1002/2014JA020481
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magnetosonic waves
Authors: Xiao Fuliang, Zhou Qinghua, He Yihua, Yang Chang, Liu Si, et al.
Title: Penetration of magnetosonic waves into the plasmasphere observed by the Van Allen Probes
Abstract: 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 an. . .
Date: 09/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL065745 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015GL065745/full
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nonlinear wave‐wave interaction
Authors: Gao Zhonglei, Su Zhenpeng, Xiao Fuliang, Summers Danny, Liu Nigang, et al.
Title: Nonlinear coupling between whistler-mode chorus and electron cyclotron harmonic waves in the magnetosphere
Abstract: Electromagnetic whistler‐mode chorus and electrostatic electron cyclotron harmonic (ECH) waves can contribute significantly to auroral electron precipitation and radiation belt electron acceleration. In the past, linear and nonlinear wave‐particle interactions have been proposed to explain the occurrences of these magnetospheric waves. By analyzing Van Allen Probes data, we present here the first evidence for nonlinear coupling between chorus and ECH waves. The sum‐frequency and difference‐frequency interactions produced the ECH sidebands with discrete frequency sweeping structures exactly corresponding to the chorus rising tones. The newly‐generated weak sidebands did not satisfy the original electrostatic wave dispersion relation. After the generation of chorus and normal ECH w. . .
Date: 11/2018 Publisher: Geophysical Research Letters DOI: 10.1029/2018GL080635 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018GL080635
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outer radiation belt
Authors: Yang Chang, Xiao Fuliang, He Yihua, Liu Si, Zhou Qinghua, et al.
Title: Storm-time evolution of outer radiation belt relativistic electrons by a nearly continuous distribution of chorus
Abstract: During the 13-14 November 2012 storm, Van Allen Probe A simultaneously observed a 10-h period of enhanced chorus (including quasi-parallel and oblique propagation components) and relativistic electron fluxes over a broad range of L = 3−6 and MLT=2 − 10 within a complete orbit cycle. By adopting a Gaussian fit to the observed wave spectra, we obtain the wave parameters and calculate the bounce-averaged diffusion coefficients. We solve the Fokker-Planck diffusion equation to simulate flux evolutions of relativistic (1.8-4.2 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∘. . .
Date: 02/2018 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL075894 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL075894/full
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Plasmaspheric Hiss
Authors: Zhu Hui, Su Zhenpeng, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Plasmatrough exohiss waves observed by Van Allen Probes: Evidence for leakage from plasmasphere and resonant scattering of radiation belt electrons
Abstract: Exohiss waves are whistler mode hiss observed in the plasmatrough region. We present a case study of exohiss waves and the corresponding background plasma distributions observed by the Van Allen Probes in the dayside low-latitude region. The analysis of wave Poynting fluxes, suprathermal electron fluxes and cold electron densities supports the scenario that exohiss leaks from the plasmasphere into the plasmatrough. Quasilinear calculations further reveal that exohiss can potentially cause the resonant scattering loss of radiation belt electrons ~Date: 02/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2014GL062964 Available at: http://doi.wiley.com/10.1002/2014GL062964
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Authors: Zhou Qinghua, Xiao Fuliang, Yang Chang, Liu Si, He Yihua, et al.
Title: Evolution of chorus emissions into plasmaspheric hiss observed by Van Allen Probes
Abstract: 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. Meanwhi. . .
Date: 05/2016 Publisher: Journal of Geophysical Research: Space Physics Pages: 4518 - 4529 DOI: 10.1002/2016JA022366 Available at: http://doi.wiley.com/10.1002/2016JA022366
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Authors: Su Zhenpeng, Zhu Hui, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: Disappearance of plasmaspheric hiss following interplanetary shock
Abstract: Plasmaspheric hiss is one of the important plasma waves controlling radiation belt dynamics. Its spatiotemporal distribution and generation mechanism are presently the object of active research. We here give the first report on the shock-induced disappearance of plasmaspheric hiss observed by the Van Allen Probes on 8 October 2013. This special event exhibits the dramatic variability of plasmaspheric hiss and provides a good opportunity to test its generation mechanisms. The origination of plasmaspheric hiss from plasmatrough chorus is suggested to be an appropriate prerequisite to explain this event. The shock increased the suprathermal electron fluxes, and then the enhanced Landau damping promptly prevented chorus waves from entering the plasmasphere. Subsequently, the shrinking magnetop. . .
Date: 03/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL063906 Available at: http://doi.wiley.com/10.1002/2015GL063906
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proton ring distribution
Authors: Xiao Fuliang, Zhou Qinghua, He Yihua, Yang Chang, Liu Si, et al.
Title: Penetration of magnetosonic waves into the plasmasphere observed by the Van Allen Probes
Abstract: 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 an. . .
Date: 09/2015 Publisher: Geophysical Research Letters DOI: 10.1002/2015GL065745 Available at: http://onlinelibrary.wiley.com/wol1/doi/10.1002/2015GL065745/full
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radial diffusion
Authors: Liu Si, Yan Qi, Yang Chang, Zhou Qinghua, He Zhaoguo, et al.
Title: Quantifying Extremely Rapid Flux Enhancements of Radiation Belt Relativistic Electrons Associated With Radial Diffusion
Abstract: 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 2 h) flux enhancements of relativistic (1.8–3.4 MeV) 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 (∼100–300 keV) 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 phas. . .
Date: 02/2018 Publisher: Geophysical Research Letters Pages: 1262 - 1270 DOI: 10.1002/grl.v45.310.1002/2017GL076513 Available at: http://onlinelibrary.wiley.com/doi/10.1002/2017GL076513/full
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Radiation belt
Authors: Chen Yaru, Zhou Qinghua, He Yihua, Yang Chang, Liu Si, et al.
Title: Global occurrences of electrostatic electron cyclotron harmonic waves associated with radiation belt electron distributions
Abstract: Electrostatic electron cyclotron harmonic (ECH) waves can yield diffuse aurora primarily at higher L‐shells by driving efficient precipitation loss of plasma sheet electrons. Here using the Van Allen Probes high resolution data, we examine in detail the global occurrences of ECH waves during the period from October 1, 2012 to June 30, 2017 and find that there are totally 419 events of enhanced ECH waves. The statistical results demonstrate that ECH waves can be present over a broad region of L=4‐6 and 00‐24 MLT, with a 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 keV. Both ECH wave events and the electron ring distributions are closely related and . . .
Date: 04/2019 Publisher: Geophysical Research Letters DOI: 10.1029/2019GL082668 Available at: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019GL082668
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Authors: Yang Chang, Su Zhenpeng, Xiao Fuliang, Zheng Huinan, Wang Yuming, et al.
Title: A positive correlation between energetic electron butterfly distributions and magnetosonic waves in the radiation belt slot region
Abstract: Energetic (hundreds of keV) electrons in the radiation belt slot region have been found to exhibit the butterfly pitch angle distributions. Resonant interactions with magnetosonic and whistler-mode waves are two potential mechanisms for the formation of these peculiar distributions. Here we perform a statistical study of energetic electron pitch angle distribution characteristics measured by Van Allen Probes in the slot region during a three-year period from May 2013 to May 2016. Our results show that electron butterfly distributions are closely related to magnetosonic waves rather than to whistler-mode waves. Both electron butterfly distributions and magnetosonic waves occur more frequently at the geomagnetically active times than at the quiet times. In a statistical sense, more distinct . . .
Date: 03/2017 Publisher: Geophysical Research Letters DOI: 10.1002/2017GL073116 Available at: http://doi.wiley.com/10.1002/2017GL073116
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