Magnetospheric chorus wave simulation with the TRISTAN-MP PIC code

Abstract

We present the results of particle-in-cell simulations of the whistler anisotropy instability that results in magnetospheric chorus wave excitation. The simulations were carried out using, for the first time for this problem, the 2D TRISTAN-massively parallelized code, widely used before in the modeling of astrophysical shocks. The code has been modified to allow for two populations of electrons: cold electrons (which maintain the wave propagation) and hot electrons (which provide the wave growth). For the hot electrons, the anisotropic form of the relativistic Maxwell-Jüttner distribution is implemented. We adopt the standard approximation of a parabolic magnetic field to simulate the Earth's magnetic field close to the equator. Simulations with different background magnetic field inhomogeneity strengths demonstrate that higher inhomogeneity yields lower frequency chirping rates and, eventually, it suppresses chorus generation. The results are in agreement with other numerical simulations and the theoretical predictions for the frequency chirping rates.