2-DIMENSIONAL MAGNETOHYDRODYNAMIC SIMULATION OF A FLOWING PLASMA INTERACTING WITH AN EXTERNALLY IMPOSED MAGNETIC-FIELD

The problem of plasma flow relative to a modulated magnetic field has been the subject of several studies. One motivation for studying this problem is the possibility of using a deliberately imposed surface of magnetic islands as a means of velocity profile control. This subject is also of importance for the study of stability against ideal and resistive magnetohydrodynamic (MHD) modes and the topic of locked modes. A two-dimensional (2-D) MHD simulation code is used to examine the behavior of a plasma flowing, in steady state, past a modulated magnetic field in "slab geometry." It is shown that at "low" velocities the stress is dominated by the Maxwell and the viscosity terms and that forces are exchanged between the plasma and the magnetic field in a narrow boundary surrounding the island. It is found that the island is suppressed when the viscous force at the separatrix exceeds the maximum force that can be supported by an island. For "high" velocities (velocities beyond the critical velocity for island suppression), the stress is dominated by the Maxwell and the Reynolds terms, and the exchange of forces is taking place in a narrow region around the point where the plasma flow velocity matches the Alfvén speed. © 1995 American Institute of Physics.