Relativistic Electron Flux Decay and Recovery: Relative Roles of EMIC Waves, Chorus Waves, and Electron Injections

Abstract We investigate the dynamics of relativistic electrons in the Earth's outer radiation belt by analyzing the interplay of several key physical processes: electron losses due to pitch angle scattering from electromagnetic ion cyclotron (EMIC) waves and chorus waves, and electron flux increases from chorus wave‐driven acceleration of 100–300 keV seed electrons injected from the plasma sheet. We examine a weak geomagnetic storm on 17 April 2021, using observations from various spacecraft, including GOES, Van Allen Probes, ERG/ARASE, MMS, ELFIN, and POES. Despite strong EMIC‐ and chorus wave‐driven electron precipitation in the outer radiation belt, trapped 0.1–1.5 MeV electron fluxes actually increased. We use theoretical estimates of electron quasi‐linear diffusion rates by chorus and EMIC waves, based on statistics of their wave power distribution, to examine the role of those waves in the observed relativistic electron flux variations. We find that a significant supply of 100–300 keV electrons by plasma sheet injections together with chorus wave‐driven acceleration can overcome the rate of chorus and EMIC wave‐driven electron losses through pitch angle scattering toward the loss cone, explaining the observed net increase in electron fluxes. Our study emphasizes the importance of simultaneously taking into account resonant wave‐particle interactions and modeled local energy gradients of electron phase space density following injections, to accurately forecast the dynamical evolution of trapped electron fluxes.

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Publication Details

Journal
Journal of Geophysical Research Space Physics
Published
2024-12-01
DOI
https://doi.org/10.1029/2024ja033174
Citations
1
Primary Topic
Ionosphere and magnetosphere dynamics
Type
article
Field-Weighted Citation Impact
0.33
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article

Relativistic Electron Flux Decay and Recovery: Relative Roles of EMIC Waves, Chorus Waves, and Electron Injections

Takefumi Mitani, Yoshiya Kasahara, Shoya Matsuda, Iku Shinohara et al.
1 citations
Journal of Geophysical Research Space Physics
Ionosphere and magnetosphere dynamics
0.33
article

Relativistic Electron Flux Decay and Recovery: Relative Roles of EMIC Waves, Chorus Waves, and Electron Injections

Takefumi Mitani, Yoshiya Kasahara, Shoya Matsuda, Iku Shinohara, Xiao‐Jia Zhang, Shoichiro Yokota, Zijin Zhang, M. Teramoto, Anton Artemyev, D. Mourenas, K. Keika, Tomoaki Hori, Ayako Matsuoka, V. Angelopoulos, Satoshi Kasahara, Yoshizumi Miyoshi, Takeshi Takashima
article en
1 citations

Abstract

Abstract We investigate the dynamics of relativistic electrons in the Earth's outer radiation belt by analyzing the interplay of several key physical processes: electron losses due to pitch angle scattering from electromagnetic ion cyclotron (EMIC) waves and chorus waves, and electron flux increases from chorus wave‐driven acceleration of 100–300 keV seed electrons injected from the plasma sheet. We examine a weak geomagnetic storm on 17 April 2021, using observations from various spacecraft, including GOES, Van Allen Probes, ERG/ARASE, MMS, ELFIN, and POES. Despite strong EMIC‐ and chorus wave‐driven electron precipitation in the outer radiation belt, trapped 0.1–1.5 MeV electron fluxes actually increased. We use theoretical estimates of electron quasi‐linear diffusion rates by chorus and EMIC waves, based on statistics of their wave power distribution, to examine the role of those waves in the observed relativistic electron flux variations. We find that a significant supply of 100–300 keV electrons by plasma sheet injections together with chorus wave‐driven acceleration can overcome the rate of chorus and EMIC wave‐driven electron losses through pitch angle scattering toward the loss cone, explaining the observed net increase in electron fluxes. Our study emphasizes the importance of simultaneously taking into account resonant wave‐particle interactions and modeled local energy gradients of electron phase space density following injections, to accurately forecast the dynamical evolution of trapped electron fluxes.

Journal of Geophysical Research Space PhysicsVol. 129(12)
Kanazawa University (JP), Planetary Science Institute (US), University of California, Los Angeles (US), The University of Texas at Dallas (US), Kyushu Institute of Technology (JP), Kyoto University (JP), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris-Saclay (FR), Japan Aerospace Exploration Agency (JP), CEA DAM Île-de-France (FR), CEA Paris-Saclay (FR), Institute of Space and Astronautical Science (JP), Nagoya University (JP), The University of Tokyo (JP), The University of Osaka (JP)
Openalex Percentile: Top 32%
Ionosphere and magnetosphere dynamics
0.33
DOISourceOpenAlex
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