The formulation of a method for the systematic computation of the growth rate of the weakly unstable resistive wall mode (RWM) in 3D configurations by using results from ideal stability codes is presented. It is shown that the growth rate of the RWM is given, approximately, by the rate at which the available free energy for the ideal external kink mode can be dissipated by the resistive wall. The eigenfunction is also approximated by that of the external kink mode. This formulation is demonstrated by coupling to the ideal MHD code KSTEP with computation of the dissipation on the resistive wall. Results of the stability of the RWM in LHD plasmas and discussion of the validity and improvement of the computation are also included.
Observation and control of resistive wall modes