M3D-K simulations of energetic particle-driven instabilities in KSTAR

Low-frequency fishbone and high-frequency chirping modes were observed in the KSTAR experiment after tangential NBI heating is turned on. Driven by these experimental phenomena, we utilize the kinetic-MHD hybrid code M3D-K to carry out simulations of beam ion-driven modes using the parameters of the KSTAR experiment. The low-frequency fishbone in the early phase of the discharge is confirmed by the simulations with the calculated frequency consistent with the experimental measurement. Nonlinear simulation results show that the low-frequency fishbone jumps to a high-frequency BAE-like mode. For the later phase of the discharge, simulation results show that high-frequency BAE modes are excited with initial frequencies similar to the measured values. In the nonlinear stage, the simulations show frequency chirping followed by frequency jumping due to the nonlinear evolution of beam ion distribution. Finally, the effects of toroidal rotation have also been investigated. Results show that mode structures of the beam-driven BAEs do not change much. The effect of toroidal rotation is mainly stabilizing. The details of simulation results and analysis will be presented.