Influence of aspect ratio, plasma viscosity, and radial position of the resonant surfaces on the plasmoid formation in the low resistivity plasma in Tokamak

In the present paper, we systematically investigate the nonlinear evolution of the resistive kink mode in the low resistivity plasma in Tokamak geometry. We find that the aspect ratio of the initial equilibrium can significantly influence the critical resistivity for plasmoid formation. With the aspect ratio of 3/1, the critical resistivity can be one magnitude larger than that in cylindrical geometry due to the strong mode-mode coupling. We also find that the critical resistivity for plasmoid formation decreases with increasing plasma viscosity in the moderately low resistivity regime. Due to the geometry of Tokamaks, the critical resistivity for plasmoid formation increases with the increasing radial location of the resonant surface.