Simulation of the collisionless tearing instability in an anisotropic neutral sheet

Abstract

A two‐dimensional magnetoinductive particle‐in‐cell code is used to compare the stability of isotropic and anisotropic current layers in a collisionless plasma. We find, in agreement with recent theories, that temperature anisotropy with T ⊥ > T ∥ significantly enhances the instability. The simulation growth rates agree well with analytical predictions of growth rates in the linear phase. Nonlinear growth rates are significantly larger than linear growth rates and are apparently the result of coalescence instability. For a fixed system length the influence of coalescence on the growth rates increases with anisotropy. This is evidently because of a shift in the most unstable mode to shorter wavelength with increasing anisotropy. Thus anisotropic current layers tend to produce large amplitude small wavelength islands which rapidly merge.