Particle simulation of current sheet instabilities under finite guide field

The instability of a Harris current sheet under a broad range of finite guide field $B_{ G}$ is investigated using a gyrokinetic electron and fully kinetic ion particle simulation code. In this particle model, the rapid electron cyclotron motion is removed, while the realistic mass ratio \textit{mi }/\textit{me}, finite electron Larmor radii, and wave-particle interactions are kept. Firstly, a linearized $\delta f$ GKe/FKi simulation is carried out in the 2-D plane containing the guide field along $y $and the current sheet normal along $z$. It is found that for a finite $B_{ G}$/$B_{ x0}\le $1, where $B_{x0}$ is the asymptotic antiparallel component of magnetic field, three unstable modes, i.e., modes A, B, and C, can be excited in the current sheet. Modes A and C, appearing to be quasielectrostatic modified two-stream instability/whistler mode, are located mainly on the edge of the current sheet. Mode B, on the other hand, is confined in the current sheet center and carries a compressional magnetic field $B_{ y}$ perturbation along the direction of electron drift velocity. In the cases with extremely large $B_{ G}$/$B_{ x0}>>$1, the wave modes evolve to a globally propagating instability. Secondly, the effects of $k_{x}$ is calculated. Finally, nonlinear $\delta f$ GKe/FKi simulation is conducted to study the nonlinear physics of the unstable modes in the current sheet..