Toroidal modeling of interaction between internal kink mode and plasma flow

Abstract

Non-linear interaction between the internal kink mode and toroidal plasma rotation is numerically studied using the MARS-Q code [Liu et al., Phys. Plasmas 20, 042503 (2013)]. Simulation results show core plasma flow damping due to various toroidal torques, generated by a weakly stable internal kink mode. The 3-D field perturbation induced torques, including the neoclassical toroidal viscous (NTV) torque, as well as that produced by the Maxwell and Reynolds stresses, act as sink terms in the toroidal momentum balance model. The NTV torque is found to play a dominant role in the flow damping in all cases considered in this study. The modification to the internal kink mode structure is observed during the flow damping. Whilst a steady state can be achieved in the coupled mode-flow evolution with a uniform initial flow, a sheared initial flow affects the linear stability of the mode and consequently changes the non-linear evolution. For cases where the steady state solution is achieved, the saturated plasma flow speed critically depends on the initial flow condition as well as the initial amplitude of the internal kink mode but is less sensitive to the on-axis safety factor q0, as long as the latter stays above 1.