Simulation and Quasi-Linear Theory of Whistler Anisotropy Instability

The whistler anisotropy (or electromagnetic electron cyclotron) instability may be operative in many geomagnetic and heliospherical environments, including the radiation belt, solar wind, and the solar corona. The present investigation carries out a comparative analysis between the two-dimensional particle-in-cell simulation of weakly growing whistler anisotropy instability and the velocity moment-based two-dimensional quasi-linear theory under the assumption of bi-Maxwellian electron distribution function. It is shown that the simplified quasi-linear theory provides a qualitative agreement with the more rigorous particle-in-cell simulation, but some discrepancies are also found. Possible causes for the differences in either method are discussed, and future improvements on the theory are suggested. Potential applicability of the present finding in the context of the space and astrophysics is discussed.