Particle-in-cell simulations of tearing modes in reversed-field-pinch-like plasma

Fully electromagnetic particle-in-cell simulations of tearing modes in two-dimensional plane geometry in a force-free reversed field pinch (RFP)-like plasma equilibrium are performed to study possible kinetic effects on these modes in RFPs. Linear tearing modes are compared in the kinetic and two fluid models. The results showed that the growth rates and the profiles of magnetic field components in the two models are very similar, indicating that the kinetic effects on the studied tearing modes are weak such that the two fluid approximation is rather accurate for modeling these instabilities in RFPs. During the nonlinear evolution of the tearing mode in this geometry, small scale secondary instabilities located near the internal layer of the primary tearing instability are excited. These secondary instabilities appear to be driven by the nonlinearly induced local pressure gradient in the regions of unfavorable curvature of the nonlinearly evolved magnetic field. They could also appear in a realistic RFP geometry and play a role during sawtooth crashes in these machines.