Abstract. Fusion power from a tokamak increases as β² (β is the ratio of the plasma and magnetic field pressures) and so the mitigation of instabilities such as the resistive wall mode (RWM), that can prevent high β operation, is important. Stabilization of the RWM with a plasma rotation frequency of below 1% Ω_A, where Ω_A is the Alfvénic rotation frequency, has been observed in a number of tokamaks. An analytical model for this stabilization, in a cylindrical plasma with a resonant layer, is discussed here. The layer theory of Porcelli (1987 Phys. Fluids 30 1734) is used to provide a model of the physics within the resonant layer. A dispersion relation connecting the plasma equilibrium to the layer physics in a rotating plasma is developed. Two mechanisms for RWM stabilization are investigated. The first includes viscosity in the resonant layer. The second assumes that stabilization occurs in the transition from one layer response to another. These models indicate a priori that there is a large parameter space where stabilization of the RWM by rotation is possible. However, if experimentally realistic timescales and rotation, namely O(1)% Ω_A, are considered then only a small window for stabilization exists. It is therefore unlikely that these mechanisms explain the observed experimental RWM stabilization. It seems that other physical effects, such as toroidal mode coupling in the outer equilibrium or pressure gradients in a toroidal geometry, will be responsible for stabilization.

Print publication: Issue 11 (November 2009)
Received 2 June 2009, in final form 17 September 2009
Published 28 October 2009