Drift waves in plasmas with sheared flows

In the standard approach to the problem of shear stabilization of drift waves the diamagnetic drift velocity v(*) is regarded as a constant, which is usually not satisfied at the edge of a tokamak plasma. In configurations of this type, with a steep density gradient and radially sheared transverse velocity field, the magnetic shear stabilization criteria are severely restricted, and the velocity profile curvature v "(0) (x) is found to play a crucial role. In the strongly nonlinear regime, unstable drift waves may saturate into stationary coherent vortex-type structures. The latter include a tripolar vortex. (C) 1998 American Institute of Physics. [S1070-664X(98)03312-6].