Kinetic versus ideal magnetohydrodynamic modelling of the resistive wall mode in a reversed field pinch plasma

Abstract

Resistive wall modes (RWMs) are studied within the kinetic model proposed by Heyn et al. [Nucl. Fusion 46, S159 (2006); Phys. Plasmas 18, 022501 (2011)], which accounts for Landau damping, transit-time magnetic pumping, and Coulomb collisions in cylindrical geometry. Results for the reversed field pinch plasma are compared to the magnetohydrodynamic results obtained by Guo et al., [Phys. Plasmas 6, 3868 (1999)]. Stabilization of the external kink mode by an ideal wall as well as stabilization of the resistive wall mode by toroidal plasma rotation is obtained. In contrast to MHD modelling, which predicts a stability window for the resistive wall position, kinetic modelling predicts a one sided window only, i.e., the resistive wall must be sufficiently close to plasma to achieve rotational stabilization of the mode but there is no lower limit on the wall position. Stabilizing rotation speeds are found somewhat smaller when compared to MHD results. In addition, for the present plasma configuration, the kinetic model predicts resistive wall mode stabilization only in one direction of toroidal rotation. In the opposite direction, a destabilizing effect is observed. This is in contrast to MHD where mode stabilization is symmetric with respect to the direction of the toroidal plasma rotation.