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Energetic electron precipitation induced by oblique whistler mode chorus emissions
  • Yi-Kai Hsieh,
  • Yoshiharu Omura,
  • Yuko Kubota
Yi-Kai Hsieh
Kyoto University

Corresponding Author:[email protected]

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Yoshiharu Omura
Kyoto University
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Yuko Kubota
Kyoto University
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Abstract

Energetic electron accelerations and precipitations in the Earth’s outer radiation belt are highly associated with wave-particle interactions between whistler mode chorus waves and electrons. We perform test particle simulation to investigate the electron behaviors interacting with both parallel and obliquely propagating chorus emissions at L=4.5. We build up a database of the Green’s functions, which are treated as results of the input electrons interacting with one emission, for a large number of electrons interacting with whistler mode chorus emissions. The loss process of electron fluxes interacting with consecutive chorus emissions in the outer radiation belt are traced by applying the convolution integrals of distribution functions and the Green’s functions. Oblique chorus emissions lead to more electron precipitation than that led by parallel chorus emissions. By checking the resonance condition and resonant energy at loss cone angle, we find that electrons are hardly dropped into the loss cone directly by Landau resonance. The nonlinear scattering via cyclotron resonance is the main process that pushes energetic electrons into the loss cone. We propose a 2-step precipitation process for oblique chorus emissions that contributes to more electron loss: (1) During the first chorus emission, the nonlinear trapping of Landau resonance moves an electron near the loss cone. (2) During the second emission, the nonlinear scattering of cyclotron resonance scatters the electron into the loss cone. The combination of Landau resonance by oblique chorus emissions and cyclotron resonance results in the higher precipitation rate than the single cyclotron resonance by purely parallel chorus emissions.
Jan 2022Published in Journal of Geophysical Research: Space Physics volume 127 issue 1. 10.1029/2021JA029583