Numerical studies for the linear growth of resistive wall modes generated by plasma flows in a slab model

Abstract

The resistive wall mode generated by plasma-wall relative rotations is studied numerically in a slab model with a compressible plasma flow parallel to the magnetic field. The linear growth of the mode is investigated with different parameters in numerical simulations. The critical plasma flow velocities for the instability are calculated as the wave number of the mode and other parameters vary. It is found that in the long wavelength regime, the critical velocity is in the range of the sound speed cs, as predicted in theory. In the short wavelength regime however, the critical velocity increases to a level of Alfvén velocity VA and a second stable region is found. This region eventually merges with the first stable region as the wave number increases and stabilizes the mode. The growth rate of the mode decreases with the wave number of the mode and the plasma viscosity. The critical wave number for the instability is also calculated as the plasma velocity changes.