Effect of sheared equilibrium plasma rotation on the classical tearing mode in a cylindrical geometry

The effect of sheared equilibrium plasma rotation on the stability of tearing modes in an Ohmic (low plasma beta) regime is investigated. It is found, by means of numerical MHD simulations in a cylindrical geometry, that plasma rotation in the equivalent toroidal direction can result either in the increase or in the decrease of the instability growth rate. Perpendicular plasma viscosity and plasma rotation shear at the modes' rational surface play a key role on assessing the effect of shear flow. While destabilizing for low viscosity plasmas (ratio of the resistive to viscous diffusion time scales tau(R)/tau(V)< 1), for viscous plasmas (tau(R)/tau(V)> 1) shear flow reduces the growth rate. Above a given threshold in the rotation shear (that depends on the ratio tau(R)/tau(V)) a tearing mode, unstable in the absence of rotation, can be stabilized. The effect of sheared toroidal flow on mode stability, in both viscosity regimes that are considered in the paper, is qualitatively independent of the aspect ratio. (c) 2007 American Institute of Physics.