Nonlinear resonant interaction of radiation belt electrons with intense whistler-mode waves

<p dir="ltr">The dynamics of the Earth’s outer radiation belt, filled by energetic electron fluxes, is largely controlled by electron resonant interactions with electromagnetic whistler-mode waves. The most coherent and intense waves resonantly interact with electrons nonlinearly, and the observable effects of such nonlinear interactions cannot be described within the frame of classical quasi-linear models.</p><p dir="ltr">This paper provides an overview of the current stage of the theory of nonlinear resonant interactions and discusses different possible approaches for incorporating these nonlinear interactions into global radiation belt simulations. We focus on observational properties of whistler-mode waves and theoretical aspects of nonlinear resonant interactions between such waves and energetic electrons. We consider only sufficiently energetic particles, which can be treated as test particles and do not have a significant feedback to the waves. The review covers two main regimes of nonlinear resonant wave-particle interactions: the regime of long wave-packets, historically better studied, and the regime of short wave-packets, actively investigated more recently based on refined spacecraft observations.</p>