Nonlinear acceleration of the electron inertia-dominated magnetohydrodynamic modes due to electron parallel compressibility

Abstract

The behavior of the collisionless magnetohydrodynamics modes is investigated by the gyrokinetic particle simulation in a cylindrical tokamak plasma in the parameter region where the effects of electron inertia and electron parallel compressibility are competitive for magnetic reconnection. Although the linear growth of the m=1 internal kink-tearing mode is dominated by the electron inertia, it is found that the growth rate can be nonlinearly accelerated due to the electron parallel compressibility proportional to the ion sound Larmor radius ρs. It is also found that, as decreasing the electron skin depth δe, the maximum growth rate before the internal collapse saturates independently of the microscopic scales such as δe and ρs. The acceleration of growth rate is also observed in the nonlinear phase of the m=2 double tearing mode.