STABILIZATION OF BALLOONING MODES WITH SHEARED TOROIDAL ROTATION

Stabilization of magnetohydrodynamic ballooning modes by sheared toroi dal rotation is demonstrated using a shifted circle equilibrium model. A generalized ballooning mode representation is used to eliminate the fast Alfven wave, and an initial value code solves the resulting equa tions. The s - alpha diagram (magnetic shear versus pressure gradient) of ballooning mode theory is extended to include rotational shear. In the ballooning representation, the modes shift periodically along the field line to the next point of unfavorable curvature. The shift freq uency (d Omega/dq, where Omega is the angular toroidal velocity and q is the safety factor) is proportional to the rotation shear and invers ely proportional to the magnetic shear. Stability improves with increa sing shift frequency and direct stable access to the second stability regime occurs when this frequency is approximately one-quarter to one- half the Alfven frequency, omega(A) = V-A/qR. (C) 1995 American Instit ute of Physics.