Electron Cyclotron Harmonic Wave Instability by Loss Cone Distribution

Liu, Xu; Chen, Lunjin; Gu, Wenyao; Zhang, Xiaojia

doi:10.1029/2018ja025925

Cited by 24 publications

(40 citation statements)

References 23 publications

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“…And, indeed, Figure e demonstrates that ECH wave intensity peaks at δB ‖ minima (i.e., during intervals of decreasing E l ). Although the peak ECH wave growth rate from this free energy source should be at small harmonic numbers (Liu et al, ; Ashour‐Abdalla & Kennel, ; Ni et al, ), THEMIS‐D observed peak ECH wave amplitudes at the fourth through seventh harmonics. Moreover, the role of loss cone anisotropy in the periodic ECH wave excitation is unclear.…”

Section: Spacecraft Data and Methodsmentioning

confidence: 99%

Periodic Excitation of Chorus and ECH Waves Modulated by Ultralow Frequency Compressions

et al. 2019

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Spacecraft observations often reveal the presence of marginally stable chorus and electron cyclotron harmonic (ECH) waves across a spatial scale about several Earth radii (R E ), which is much larger than the spatial scale of the localized injections that are thought to generate them. Given the importance of these waves for electron acceleration, scattering, and loss to the atmosphere, here we investigate how such broad, periodic wave excitation might occur. We show that it can be attributed to modulation of hot (resonant) electron distributions by ultralow frequency (ULF) waves, which transport electrons radially inward/outward by as much as ∼1.5 R E . Unstable electrons (and chorus waves generated by them) from higher L-shells (presumably from the azimuthally extended flow-braking region) are thus brought to lower L-shells. Half a ULF cycle later, outward electron transport increases the loss cone anisotropy (the perpendicular velocity gradient near the loss cone), resulting in periodic generation of ECH waves with intensities that are anticorrelated with chorus wave intensity. Such wave generation and intermittent electron precipitation (modulated on the spatial/temporal scale of a ULF wavelength/wave period) across large spatial scales could explain the pulsating aurora.

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Section: Spacecraft Data and Methodsmentioning

confidence: 99%

Periodic Excitation of Chorus and ECH Waves Modulated by Ultralow Frequency Compressions

et al. 2019

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“…For the sake of completeness, we list the electrostatic electron cyclotron harmonic waves for minor resonant interactions with radiation belt electrons and a contribution to diffuse aurora at L > 8 (Liu et al, ; Meredith et al, ; Meredith, Horne, Thorne, & Anderson, ; Shaw & Gurnett, ; Zhang et al, ).…”

Section: Particle Loss In the Inner And Outer Zonesmentioning

confidence: 99%

Particle Dynamics in the Earth's Radiation Belts: Review of Current Research and Open Questions

et al. 2020

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The past decade transformed our observational understanding of energetic particle processes in near‐Earth space. An unprecedented suite of observational systems was in operation including the Van Allen Probes, Arase, Magnetospheric Multiscale, Time History of Events and Macroscale Interactions during Substorms, Cluster, GPS, GOES, and Los Alamos National Laboratory‐GEO magnetospheric missions. They were supported by conjugate low‐altitude measurements on spacecraft, balloons, and ground‐based arrays. Together, these significantly improved our ability to determine and quantify the mechanisms that control the buildup and subsequent variability of energetic particle intensities in the inner magnetosphere. The high‐quality data from National Aeronautics and Space Administration's Van Allen Probes are the most comprehensive in situ measurements ever taken in the near‐Earth space radiation environment. These observations, coupled with recent advances in radiation belt theory and modeling, including dramatic increases in computational power, have ushered in a new era, perhaps a “golden era,” in radiation belt research. We have edited a Journal of Geophysical Research: Space Science Special Collection dedicated to Particle Dynamics in the Earth's Radiation Belts in which we gather the most recent scientific findings and understanding of this important region of geospace. This collection includes the results presented at the American Geophysical Union Chapman International Conference in Cascais, Portugal (March 2018) and many other recent and relevant contributions. The present article introduces and review the context, current research, and main questions that motivate modern radiation belt research divided into the following topics: (1) particle acceleration and transport, (2) particle loss, (3) the role of nonlinear processes, (4) new radiation belt modeling capabilities and the quantification of model uncertainties, and (5) laboratory plasma experiments.

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“…PLEASE CITE THIS ARTICLE AS DOI: 10.1063/5.0002336 perpendicular direction. 33 We calculated f (v||, v⊥) at the position where nearly the peak plasma density was observed (x = 0 mm, y = 5.0 mm, and z = 2.0 mm). In the velocity phase space, the following relation for the trapped electron is derived: 34…”

Section: Loss Cone Of the Magnetic Mirrormentioning

confidence: 99%