Electron Resonant Interaction With Coherent ULF Waves: Hamiltonian Approach

Abstract

AbstractElectron resonant interaction with ultra‐low‐frequency (ULF) waves is considered to be a driver of electron radial transport in Earth’s inner magnetosphere. Traditional concept of such interaction assumes the electron slow diffusive scattering by a broad‐band ULF spectrum, but recent spacecraft observations reported a possibility for electrons to resonate nonlinearly with intense coherent ULF waves. This study proposes a theoretical model describing the main elements of such nonlinear resonant interactions. We implement a Hamiltonian approach to describe equatorial electron motion in a dipole magnetic field and electric ULF wavefield and demonstrate the ULF‐electron interactions has two basic nonlinear resonant regimes: phase bunching and phase trapping. Finally, we discuss possible applications of the proposed theoretical approach and the importance of ULF‐electron nonlinear resonances.