Scattering by whistler-mode waves during a quiet period perturbed by substorm activity
- Alternative Energies and Atomic Energy Commission (CEA), Arpajon (France); Alternative Energies and Atomic Energy Commission (CEA), Bruyeres-le-Chatel (France)
- New Mexico Consortium, Los Alamos, NM (United States); Space Science Institute, Boulder, CO (United States)
- Univ. of Iowa, Iowa City, IA (United States)
- New Mexico Consortium, Los Alamos, NM (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Univ. of Colorado, Boulder, CO (United States)
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Charles Univ., Prague (Czech Republic); Czech Academy of Sciences, Prague (Czech Republic)
- Office National d'Études et de Recherches Aérospatiales (ONERA), Palaiseau (France)
- Aerospace Corporation, El Segundo, CA (United States)
- Johns Hopkins Univ., Baltimore, MD (United States)
We study the dynamics of radiation belt electrons during a 10-day quiet period perturbed by substorm activity and preceding a high-speed stream (HSS), aiming at a global description of the radiation belts in L-shell, L in [2, 6], and energy [0.1, 10] MeV. We combine Van Allen Probes observations and Fokker-Planck numerical simulations of pitch-angle diffusion. The Fokker-Planck model uses event-driven pitch angle diffusion coefficients from whistler-mode waves, built from the wave properties and the ambient plasma density measurements from the Van Allen Probes. We first find this event has some similar characteristics to regular quiet times previously studied; a widely extended plasmasphere within which we observe strong and varying whistler-mode waves. These ambient conditions lead to strong pitch-angle scattering, which contributes to the creation of a wide slot region as well as a significant decay of the outer radiation belts, which are observed and qualitatively well simulated. In addition, we find the substorm activity causes short duration (within ± 4h) decay of the plasma density and a lowering amplitude of the whistler-mode waves within the plasmasphere, both causing opposite effects in terms of pitch angle diffusion. This leads to a diminution of pitch-angle diffusion at the time of the main substorm activity. Conversely, whistler-mode waves become enhanced in the time periods between the substorm injections. All effects cumulated, we find an enhancement of pitch angle diffusion by whistler-mode waves above L~4.7 during the 10-day period. This directly relates to the combination of quietness and substorm activity which allows pitch angle diffusing of up to 1 MeV electrons in the outer belt. Relativistic electrons of 1–2 MeV remain trapped in the outer belt, from L~4.7 to L~5.2, forming, in both the observations and the simulations, a distinct pocket of remnant electrons.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE; JHU/APL; MEYS; National Aeronautics and Space Administration (NASA)
- Grant/Contract Number:
- 89233218CNA000001
- OSTI ID:
- 1832383
- Alternate ID(s):
- OSTI ID: 1811095
- Report Number(s):
- LA-UR--21-23197
- Journal Information:
- Journal of Atmospheric and Solar-Terrestrial Physics, Journal Name: Journal of Atmospheric and Solar-Terrestrial Physics Vol. 215; ISSN 1364-6826
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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