Impact of plasma rotation on the linear physics of resistive wall modes in tokamaks

Aiba, Nobuyuki; Shiraishi, Junya; Hirota, Makoto

The authors identified that plasma poloidal rotation sometimes plays an important role for ideal MHD stability due to changing the Doppler-shift frequency. As the result, the stability of edge localized MHD mode can depends on the direction of toroidal rotation; this dependence is qualitatively consistent with the experimental results observed in JT-60U. Plasma rotation is also responsible for the stability of resistive wall mode (RWM). In reversed shear plasmas, plasma rotation once stabilize this RWM but destabilize this again when rotation frequency reaches to certain frequency. This re-destabilization is thought to be related to the coupling between RWM and a stable MHD wave; this coupling is one of the destabilizing mechanisms discussed in previous theoretical papers. This re-destabilized RWM can become unstable in the plasma whose beta value is below no-wall beta limit.