Computer experiment of cyclotron interaction for chorus generation

Chorus emissions have been frequently observed by the GEOTAIL spacecraft around the equatorial plane in the dayside outer magneto-sphere. Chorus emissions are the plasma waves generated via the interaction between wave and particle, so their generation and propagation mechanisms are very complicated. In this study, by means of theoretical analysis and particle simulation, we investigate the cyclotron resonance and pitch-angle diffusion of the resonant electrons, to analyze the generation mechanism of the chorus emissions. The results indicate that the initially large pitch-angle anisotropy of the resonant electrons are rapidly pitch-angle diffused by a generated whistler mode wave, and the pitch-angle anisotropy decreases down to the small anisotropy which saturates wave growth.