Nonlinear gyrokinetic simulations of tearing instability

We present numerical results of nonlinear tearing mode simulations in a strong guide magnetic field limit using the \texttt{AstroGK} astrophysical gyrokinetics code. From the comparative study of linear tearing mode between gyrokinetics and two-fluid MHD, significant discrepancy of the growth rate scaling have been observed in relatively high-beta plasmas [1] while they show good agreement in low-beta. Since the Alfv\'en wave dynamics is coupled with the ion sound wave dynamics in high-beta plasmas, it is required to solve parallel ion dynamics kinetically rather than assuming simple adiabatic relations. In this work, we extend our study of the tearing mode to the nonlinear stage where discrepancy between gyrokinetics and fluid models is expected to become more significant. We discuss magnetic island evolution, saturation, and plasma heating due to magnetic reconnection in high-beta plasmas.\\[4pt] [1] R. Numata et al., Phys. Plasmas \textbf{18}, 112106 (2011).