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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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Generation and Impacts of Whistler‐Mode Waves During Energetic Electron Injections in Jupiter's Outer Radiation Belt
Abstract Energetic particle injections are commonly observed in Jupiter's magnetosphere and have important impacts on the radiation belts. We evaluate the roles of electron injections in the dynamics of whistler‐mode waves and relativistic electrons using Juno measurements and wave‐particle interaction modeling. The Juno spacecraft observed injected electron flux bursts at energies up to 300 keV atMshell ∼11 near the magnetic equator during perijove‐31. The electron injections are related to chorus wave bursts at 0.05–0.5fcefrequencies, wherefceis the electron gyrofrequency. The electron pitch angle distributions are anisotropic, peaking near 90° pitch angle, and the fluxes are high during injections. We calculate the whistler‐mode wave growth rates using the observed electron distributions and linear theory. The frequency spectrum of the wave growth rate is consistent with that of the observed chorus magnetic intensity, suggesting that the observed electron injections provide free energy to generate whistler‐mode chorus waves. We further use quasilinear theory to model the impacts of chorus waves on 0.1–10 MeV electrons. Our modeling shows that the chorus waves could cause the pitch angle scattering loss of electrons at <1 MeV energies and accelerate relativistic electrons at multiple MeV energies in Jupiter's outer radiation belt. The electron injections also provide an important seed population at several hundred keV energies to support the acceleration to higher energies. Our wave‐particle interaction modeling demonstrates the energy flow from the electron injections to the relativistic electron population through the medium of whistler‐mode waves in Jupiter's outer radiation belt.
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- Award ID(s):
- 2402179
- PAR ID:
- 10617703
- Publisher / Repository:
- Journal of Geophysical Research: Space Physics
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 129
- Issue:
- 7
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1029/2024JA032624
