Synergistic effect of Coriolis and centrifugal forces from poloidal flow on internal kink and fishbone modes in tokamak plasmas

Abstract

The synergy of Coriolis force and centrifugal force is proposed to study the influence of poloidal plasma rotation on internal kink and fishbone modes. A new dispersion relation is established by making use of energy principle when Coriolis and centrifugal forces are taken into account in the momentum equation. The significant discovery is that the destabilizing (stabilizing) effect of poloidal flow on internal kink (fishbone) mode is greatly increased due to the synergy of Coriolis and centrifugal forces. Poloidal flow can neither effectively destabilize internal kink mode nor stabilize fishbone mode with any one of both centrifugal force and Coriolis force being excluded. It is most interesting that the internal kink mode, being stable with positive δWc (perturbed potential energy of bulk plasma), is unstable when poloidal rotation frequency exceeds a threshold. It is difficult for poloidal flow without shear to destabilize the internal kink mode with δWc > 0. The physical mechanism of poloidal flow destabilization of internal kink mode mainly comes from the modification of plasma inertial due to Coriolis and centrifugal forces.