Simulation of Current Sheet Instabilities Using Gygokinetic Electron and Fully Kinetic Ion Particle Code

A novel gyrokinetic electron and fully kinetic ion (GKe/FKi) particle simulation model has been developed [Lin et al., PPCF, 2005] for the purpose of investigation of magnetic reconnection in collisionless plasmas. In this model, the rapid electron cyclotron motion is removed, while retaining the finite electron Larmor radii, wave-particle interaction, and off-diagonal components of the electron pressure tensor. This treatment results in a larger time step and allows one to treat the realistic ion-to-electron mass ratio mi/me in a large-scale system. The model is particularly suitable for ω < Ωe and k∥/ k⊥<1, and for problems in which the wave modes ranging from Alfven waves to lower-hybrid/whistler waves need to be handled on an equal footing. In this talk, we introduce the GKe/FKi model and present our simulation of instabilities of Harris sheet under a broad range of finite guide field BG and with a realistic mi/me using the linearized δ f GKe/FKi code [Wang et al., PoP, 2008]. The simulation is carried out in the 2-D plane containing the guide field in the y direction and the current sheet normal along z. For a finite BG/Bx0<1, where Bx0 is the asymptotic anti-parallel field component, quasi-electrostatic modified two-stream instability/whistler mode are found on the edge of current sheet. In addition, a new mode is found to be confined in the sheet center and carry a compressional δ By along the direction of electron drift, and may contribute directly to the electron anomalous resistivity in reconnection. For BG/Bx0≫1, the wave modes evolve to a globally propagating instability. The presence of finite BG is found to modify the physics of current sheet significantly.