Toroidal Resonance of Energetic Ions and Magnetohydrodynamic Ballooning Mode Stability in Tokamaks

Abstract

Excitation of resonant mode of energetic particles and their effect on the magnetohydrodynamic (MHD) ballooning mode in tokamaks are studied by evaluating the dispersion relation derived from the modified ballooning mode equation which includes the kinetic effect of energetic ions. The kinetic effect is evaluated by solving the gyrokinetic equation for non-periodic and periodic passing particles and trapped particles. The periodic component of energetic passing ions is found to make important contribution in the inertial region, and stabilizes the MHD ballooning mode. At the MHD ballooning mode marginal stability condition, the toroidal resonant mode becomes unstable above a threshold of the energetic passing ion contribution. This toroidal resonant mode is further destabilized in the presence of the bulk plasma fluid effect.