Stability of relativistic electron trapping by strong whistler or electromagnetic ion cyclotron waves
Abstract
In the present paper, we investigate the trapping of relativistic electrons by intense whistler-mode
waves or electromagnetic ion cyclotron waves in the Earth’s radiation belts. We consider the
non-resonant impact of additional, lower amplitude magnetic field fluctuations on the stability of
electron trapping. We show that such additional non-resonant fluctuations can break the adiabatic
invariant corresponding to trapped electron oscillations in the effective wave potential. This
destruction results in a diffusive escape of electrons from the trapped regime of motion and thus
can lead to a significant reduction of the efficiency of electron acceleration. We demonstrate that
when energetic electrons are trapped by intense parallel or very oblique whistler-mode waves,
non-resonant magnetic field fluctuations in the whistler-mode frequency range with moderate
amplitudes around 3 15 pT (much less intense than the primary waves) can totally disrupt the
trapped motion. However, the trapping of relativistic electrons by electromagnetic ion cyclotron
waves is noticeably more stable. We also discuss how the proposed approach can be used to
estimate the effects of wave amplitude modulations on the motion of trapped particles.
Origin : Publisher files allowed on an open archive
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