Nonlinear pitch angle scattering and trapping of energetic particles during Landau resonance interactions with whistler mode waves

Abstract

The time averaged equations of motion derived by Inan and Tkalcevic (1982) are used in a test particle study of Landau resonant interactions of whistler mode waves and energetic particles in the magnetopshere. By computing individual particle trajectories it is shown that the pitch angle scattering and energy exchange is significantly different for the two classes of particles, trapped and untrapped. The trapped particles are characterized by a bounded phase variation, whereas the nontrapped particles exhibit unbounded phase variation. The threshold wave electric field intensities necessary for trapping are determined. Full distribution test particle simulation is carried out to determine the precipitated electron flux that would be induced as a result of these interactions. It is shown that for typical parameters the resulting precipitation fluxes for Landau resonance interactions are much smaller than those induced in gyroresonance interactions, even for wave field intensities that are much higher than the trapping threshold.