Full particle simulation of whistler-mode chorus emissions in the magnetosphere

We perform a numerical simulation by one-dimensional electromagnetic full particle code to study the generation mechanism of whistler-mode chorus emissions in the equatorial region of the magnetosphere. As a model along the ambient magnetic field strength in the vicinity of the equator, we assume a parabolic variation of dipole. We have cold thermal electrons and relatively low anisotropic hot electrons with loss cone as plasma particles. In the initial phase, the whistler-mode waves originated in background thermal noise interact with counter-streaming anisotropic hot electrons. The amplitude growth of the incoherent whistler- mode waves is determined by the linear growth rate. When the wave amplitude reaches a certain level, the chorus elements consisting of coherent phase in the vicinity of the magnetic equator grow rapidly, and their enhanced wave packets propagate from the magnetic equator toward both hemisphere. The frequency sweep rates of the consecutively excited rising chorus elements decrease gradually. We find a threshold of wave amplitude for nonlinear growth of chorus elements. The comparison between the wave amplitude and the frequency sweep rate of rising chorus elements in the simulation fully support the nonlinear wave growth theory for generating of chorus emissions.