Zhonglei Gao

Changsha University of Science and Technology

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Fuliang Xiao

Changsha University of Science and Technology

Zhenpeng Su

University of Science and Technology of China

Si Liu

Foshan University

Chang Yang

Changsha University of Science and Technology

Yuming Wang

University of Science and Technology of China

Qinghua Zhou

Zhejiang University of Technology

Shui Wang

Shanghai Normal University

Huinan Zheng

University of Science and Technology of China

Yihua He

Changsha University of Science and Technology

Nigang Liu

Sun Yat-sen University

Cooperative Institutions

Changsha University of Science and Technology

Chinese Academy of Sciences

University of Science and Technology of China

Harbin Institute of Technology

Nagoya University

John Wiley & Sons (United States)

National Space Science Center

Kanazawa University

Kyoto University

Charles River Laboratories (Netherlands)

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Nonlinear Coupling Between Whistler‐Mode Chorus and Electron Cyclotron Harmonic Waves in the Magnetosphere

Geophysical Research Letters (2018)

Zhonglei Gao Zhenpeng Su Fuliang Xiao Danny Summers Nigang Liu

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 waves by hot electron instabilities, the nonlinear wave‐wave interactions could additionally redistribute energy among the resonant waves, potentially affecting to some extent the magnetospheric electron dynamics.

Chorus

Whistler

Dispersion relation

Harmonic

Electron precipitation

10.1029/2018gl080635

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Citations (16)

Local Generation of High‐Frequency Plasmaspheric Hiss Observed by Van Allen Probes

Geophysical Research Letters (2019)

Zhaoguo He Lunjin Chen Xu Liu Hui Zhu Si Liu

Abstract The generation of a high‐frequency plasmaspheric hiss (HFPH) wave observed by Van Allen Probes is studied in this letter for the first time. The wave has a moderate power spectral density (∼10 −6 nT 2 /Hz), with a frequency range extended from 2 to 10 kHz. The correlated observations of waves and particles indicate that HFPH is associated with the enhancement of electron flux during the substorm on 6 January 2014. Calculations of the wave linear growth rate driven by the fitted electron phase space density show that the electron distribution after the substorm onset is efficient for the HFPH generation. The energy of the contributing electrons is about 1–2 keV, which is consistent with the observation. These results support that the observed HFPH is likely to be generated locally inside the plasmasphere due to the instability of injected kiloelectron volt electrons.

Substorm

Plasmasphere

Hiss

Van Allen Probes

Local time

Lower hybrid oscillation

10.1029/2018gl081578

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Citations (32)

Ultra-low-frequency wave-driven diffusion of radiation belt relativistic electrons

Nature Communications (2015)

Zhenpeng Su Hui Zhu Fuliang Xiao Qiugang Zong Xu‐Zhi Zhou

Abstract Van Allen radiation belts are typically two zones of energetic particles encircling the Earth separated by the slot region. How the outer radiation belt electrons are accelerated to relativistic energies remains an unanswered question. Recent studies have presented compelling evidence for the local acceleration by very-low-frequency (VLF) chorus waves. However, there has been a competing theory to the local acceleration, radial diffusion by ultra-low-frequency (ULF) waves, whose importance has not yet been determined definitively. Here we report a unique radiation belt event with intense ULF waves but no detectable VLF chorus waves. Our results demonstrate that the ULF waves moved the inner edge of the outer radiation belt earthward 0.3 Earth radii and enhanced the relativistic electron fluxes by up to one order of magnitude near the slot region within about 10 h, providing strong evidence for the radial diffusion of radiation belt relativistic electrons.

Ultra low frequency

Van Allen Probes

Chorus

10.1038/ncomms10096

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Citations (86)

Responses of geostationary orbit energetic electron fluxes to chorus waves under different geomagnetic conditions

Science China Earth Sciences (2013)

Xiaoping Zhou Fuliang Xiao Yihua He Chang Yang Qinghua Zhou

Substorm

Van Allen Probes

Chorus

10.1007/s11430-013-4688-0

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Citations (1)

Nonstorm time dropout of radiation belt electron fluxes on 24 September 2013

Journal of Geophysical Research Space Physics (2016)

Zhenpeng Su Zhonglei Gao Hui Zhu Wen Li Huinan Zheng

Abstract Radiation belt electron flux dropouts during the main phase of geomagnetic storms have received increasing attention in recent years. Here we focus on a rarely reported nonstorm time dropout event observed by Van Allen Probes on 24 September 2013. Within several hours, the radiation belt electron fluxes exhibited a significant (up to 2 orders of magnitude) depletion over a wide range of radial distances ( L > 4.5), energies (∼500 keV to several MeV) and equatorial pitch angles (0°≤ α e ≤180°). STEERB simulations show that the relativistic electron loss in the region L = 4.5–6.0 was primarily caused by the pitch angle scattering of observed plasmaspheric hiss and electromagnetic ion cyclotron waves. Our results emphasize the complexity of radiation belt dynamics and the importance of wave‐driven precipitation loss even during nonstorm times.

Hiss

Van Allen Probes

Pitch angle

Electron precipitation

Electron scattering

10.1002/2016ja022546

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Citations (58)

Comprehensive Observations of Substorm‐Enhanced Plasmaspheric Hiss Generation, Propagation, and Dissipation

Geophysical Research Letters (2020)

Nigang Liu Zhenpeng Su Zhonglei Gao Huinan Zheng Yuming Wang

Abstract Plasmaspheric hiss is an important whistler‐mode emission shaping the Van Allen radiation belt environment. How the plasmaspheric hiss waves are generated, propagate, and dissipate remains under intense debate. With the five spacecraft of Van Allen Probes, Exploration of energization and Radiation in Geospace (Arase), and Geostationary Operational Environmental Satellites missions at widely spaced locations, we present here the first comprehensive observations of hiss waves growing from the substorm‐injected electron instability, spreading within the plasmasphere, and dissipating over a large spatial scale. During substorms, hot electrons were injected energy‐dispersively into the plasmasphere near the dawnside and, probably through a combination of linear and nonlinear cyclotron resonances, generated whistler‐mode waves with globally drifting frequencies. These waves were able to propagate from the dawnside to the noonside, with the frequency‐drifting feature retained. Approximately 5 hr of magnetic local time away from the source region in the dayside sector, the wave power was dissipated to of its original level.

Hiss

Plasmasphere

Substorm

Whistler

Van Allen Probes

Electrojet

10.1029/2019gl086040

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Citations (26)

Observation and Fully Thermal Simulation of Quasi‐Electrostatic Magnetosonic Waves

Geophysical Research Letters (2021)

Zhonglei Gao Si Liu Fuliang Xiao Qinghua Zhou Qian He

Abstract Magnetosonic (MS) waves are generally considered as electromagnetic harmonic fluctuations below the lower hybrid frequency. Here we present a correlated observation of proton ring‐like distribution and low harmonic magnetosonic waves with undetectable magnetic components (called QEMS). We conduct fully thermal simulations (WHAMP) to investigate the wave properties. The calculated growth rates can reproduce the observed spectral characteristics and demonstrate that the QEMS waves are excited as ion Bernstein modes by proton ring‐like distribution. The ratios between the wave electric and magnetic amplitudes E / B given by WHAMP indicate that the magnetic spectral densities are below the instrument noise level, and the ratios are ∼7–80 times larger than the wave phase speeds V ph , suggesting that the QEMS waves are essentially quasi‐electrostatic, not just visually quasi‐electrostatic due to the measurement limit. This study provides further insights into the QEMS natures.

Harmonic

10.1029/2021gl095757

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Citations (12)

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

Journal of Geophysical Research Space Physics (2019)

Geng Wang Tielong Zhang Zhonglei Gao Mingyu Wu Guoqiang Wang

Abstract Electromagnetic ion cyclotron (EMIC) waves are important for the loss of high‐energy electrons in the radiation belt. Based on the measurements of Van Allen Probes, two events during the same storm period are presented to study the propagation of EMIC waves. In the first event, left‐handed polarized EMIC waves were observed near the plasmapause, while right‐handed waves were observed in the inner plasmasphere. The Poynting flux of the right‐hand waves was mainly directed inward and equatorward, and no positive growth rates were obtained in the region of these right‐hand waves, indicating the inward propagation of the waves from a higher L ‐shell. In the second event, the wave vectors were quasi‐perpendicular to the background magnetic field inside the plasmaspheric plume but became quasi‐parallel outside. This phenomenon can be explained by the refraction of the large density gradient, which qualitatively satisfies Snell's law. These observations provide indirect evidence of the inward propagation of the EMIC waves and give a new insight on how density gradients may modify wave properties.

Plasmasphere

10.1029/2019ja027055

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Citations (10)

Rapid Landau Heating of Martian Topside Ionospheric Electrons by Large‐Amplitude Magnetosonic Waves

Geophysical Research Letters (2020)

Zhenpeng Su Nigang Liu Zhonglei Gao Bin Wang Huinan Zheng

Abstract Atmospheric escape is a fundamental process in the long‐term habitability evolution of terrestrial planets. Recent observations on Mars have found the concurrence of the severe ionospheric erosion and the large‐amplitude, quasi‐perpendicular magnetosonic waves. However, whether and then how these magnetosonic waves had contributed to the ionospheric erosion remains unclear. Here we propose a new candidate mechanism, electron Landau heating by magnetosonic waves, for the Martian ionospheric erosion. In contrast to the cyclotron resonance with oxygen atomic and molecular ions above the escape energies, the magnetosonic waves Landau‐resonate with the thermal electrons at energy channels of the order of 0.01–0.1 eV. Through the Landau resonance over tens of minutes, the large‐amplitude (12 nT) magnetosonic waves can heat the topside ionospheric electrons to ∼ 2 times the normal temperature. The topside ionospheric electron heating could result in the enhancement of the ambipolar electric potential and eventually facilitate the escape of ionospheric plasma.

Landau damping

10.1029/2020gl090190

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Citations (8)

Excitation of Highly Oblique Lower Band and Upper Band Chorus by a Loss Cone Feature and Temperature Anisotropy Distribution

Geophysical Research Letters (2019)

Qinghua Zhou Chang Yang Yihua He Si Liu Zhonglei Gao

Abstract 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 23:00–24:00 UT 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.

Chorus

10.1029/2018gl081379

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Citations (4)