Nonlinear Evolution of Shear Flows in Double Tearing Modes

Shear flows induced by the nonlinear evolution of double tearing modes in plasma are studied numerically within the framework of resistive magnetohydrodynamic theory in a slab geometry. Taking into account the plasma resistivity and the distance between two resonant surfaces in a tokamak device, the results show that the effective shear flows are generated in the magnetic island region during the process of magnetic reconnection and last for a few tens of Alfvén time. Furthermore, a few vortical structures of shear flows appear in the final stage of magnetic reconnection. A larger plasma resistivity promotes the process of magnetic reconnection while has no obvious effect on shear flows, particularly in the fast-magnetic-reconnection phase. The amplitude of the shear flows is found to increase with the increase of the initial separation between both resonant surfaces. The temporal evolution of the poloidal plasma flows is also studied in this paper.