Destabilizing effect of plane Couette flow

In contrast to its well-known stabilization of the low-frequency plasma motions, a shear flow may equally effectively destabilize a class of plasma modes. The latter quality of the flow is illustrated by studying an incompressible ideal plasma with a simple velocity profile (Couette flow in a finite interval); it is found that interchange modes are driven more unstable through their interactions with the shear flow. In the presence of the flow shear, the. growth rate of the perturbation increases due to the coupling of the Alfven wave with a Rayleigh-Taylor-type instability drive. Marginally stable modes in the flowless equilibrium achieve their maximum growth rate when the maximum flow velocity becomes comparable to the Alfven velocity. At larger shear flow velocities, however, the stabilizing "stretching" effect becomes dominant and the instability is quenched. (C) 2003 American Institute of Physics.