Plasma Rotation Effects on the Trigger of Reversed Shear Plasma Disruptions

Plasma rotation effects on the trigger and evolution of MHD modes in a reversed shear profile are studied by nonlinear MHD simulations. It is found that, in rotating plasma, magnetic islands formed around inner and outer magnetic resonant surfaces, which are stable for the tearing mode, by an external perturbation, (driven magnetic island) evolve with different growth rates during an initial growth phase. After an initial growth phase, an outer magnetic island grows explosively earlier and triggers an explosive growth of an inner one. At a final phase, enlarged magnetic islands flatten a q-profile in wide radial region including the plasma center. Though this final phase resembles closely a nonlinear destabilization of a spontaneous double tearing mode (DTM) [1], this process can explain time delay of a plasma edge oscillation to trigger an internal MHD events and disruption in RS plasmas[2].