Nonlinear Evolution of the Resistive MHD Modes in a Toroidal Plasma

Abstract

The nonlinear stabilities of resistive MHD modes are investigated in a tokamak configuration by a three dimensional MHD simulation based on a rectangular column model under the fixed boundary condition. The m=1 internal resistive kink mode is excited for the central safety factor, q₀<1, resulting in a sawtooth oscillation of temperature. Only the m=2 mode is excited for q₀<2 and a small resistivity. On the other hand, the several modes of (−m : n)=(2 : 1), (1 : 1) and (3 : 2) appear for q₀<2 and a little large resistivity depending on the q-configuration through the variation of toroidal current. The (3 : 2) mode plays an important role on the mode coupling between the (1 : 1) and (2 : 1) modes. As the result, the (2 : 1) mode finally determines the stability and stable configurations of plasma are formed with the condition of q\gtrsim2.