Weak turbulence in radiation belts

Abstract

Weak turbulence of electromagnetic waves can play a significant role in the structure and dynamics of space plasmas. It will be shown that induced nonlinear scattering dominates the dynamics in the low-beta isothermal radiation belt plasma in the Earth's magnetosphere and can dramatically affect the propagation characteristics of waves. Specifically, as the whistlers propagate away from the Earth they can be scattered in the magnetosphere such that their trajectories are turned back towards the ionosphere where they can be reflected. Repeated scattering and reflection of the magnetospherically reflected whistlers establishes a cavity in which whistler wave energy can be maintained for a longer duration with smaller wave-normal angles. Consequently, the wave-particle resonance time increases, leading to enhanced pitch angle scattering rate. Enhanced pitch angle scattering of trapped electrons into the radiation belt loss cone lowers the lifetime of the trapped particle population. Also, pitch angle scattering of the trapped population in the cavity with a loss cone distribution can amplify the whistler waves and promote a more rapid pitch angle scattering through a positive feedback mechanism. Typical storm-pumped radiation belt parameters and laboratory experiments will be used to elucidate this phenomenon.