Gyrokinetic simulations of collisionless tearing modes

Abstract

We investigate the effects of temperature and density gradients on collisionless magnetic reconnection by means of PIC-δf simulations with standard gyrokinetic equations using gyrokinetic ions and drift kinetic electrons. In a slab model ion and electron temperature gradients act stabilising on the tearing mode instability in the cases that have been considered. An additional ion and electron density gradient completely stabilises the mode below a critical η (ratio of temperature gradient to density gradient). The critical η becomes larger with decreasing equilibrium current.Nonlinear single-mode simulations show that the island width saturates at the level predicted by [1], if the linear instability growth rate is sufficiently small. Including ion and electron temperature and density gradients in nonlinear calculations the saturated island width vanishes below a critical η.