Sub-MeV Electron Precipitation Driven by EMIC Waves Through Nonlinear Fractional Resonances

0585595 - ÚFA 2025 RIV US eng J - Journal Article
Hanzelka, Miroslav - Li, W. - Qin, M. - Capannolo, L. - Shen, X. - Ma, Q. - Gan, L. - Angelopoulos, V.
Sub-MeV Electron Precipitation Driven by EMIC Waves Through Nonlinear Fractional Resonances.
Geophysical Research Letters. Roč. 51, č. 8 (2024), č. článku e2023GL107355. ISSN 0094-8276. E-ISSN 1944-8007
Institutional support: RVO:68378289
Keywords : ion-cyclotron waves * van allen probes * acceleration * diffusion * Earth's radiation belts * EMIC waves * resonant scattering * nonlinear interaction * nonresonant scattering * electron precipitation
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 5.2, year: 2022
Method of publishing: Open access
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL107355

Electromagnetic ion cyclotron waves in the Earth's outer radiation belt drive rapid electron losses through wave-particle interactions. The precipitating electron flux can be high in the hundreds of keV energy range, well below the typical minimum resonance energy. One of the proposed explanations relies on nonresonant scattering, which causes pitch-angle diffusion away from the fundamental cyclotron resonance. Here we propose the fractional sub-cyclotron resonance, a second-order nonlinear effect that scatters particles at resonance order n = 1/2, as an alternate explanation. Using test-particle simulations, we evaluate the precipitation ratios of sub-MeV electrons for wave packets with various shapes, amplitudes, and wave normal angles. We show that the nonlinear sub-cyclotron scattering produces larger ratios than the nonresonant scattering when the wave amplitude reaches sufficiently large values. The ELFIN CubeSats detected several events with precipitation ratio patterns matching our simulation, demonstrating the importance of sub-cyclotron resonances during intense precipitation events.
Permanent Link: https://hdl.handle.net/11104/0353388


Research data: GRL - Supporting Information S1