Magnetohydrodynamic-kinetic hybrid simulation of Alfvén instabilities in ICRH experiments on EAST

Abstract Nonlinear simulations of Alfvénic instabilities in EAST Ion Cyclotron Resonance Heating experiments are carried out using the magnetohydrodynamic-kinetic hybrid code MEGA. Multi- n simulations identify unstable energetic particle modes (EPMs) with toroidal mode numbers n = 1 and n = 2 , along with an n = 3 toroidal Alfvén eigenmode (TAE), all of which collectively induce measurable fast-ion redistribution. The resonant excitation mechanisms for both trapped and co-current passing fast ions are elucidated. Nonlinear analysis reveals frequency bifurcation, with the mode evolving into high-frequency TAE and low-frequency BAE-like branches via upward and downward chirping. Phase-space diagnostics directly visualize the wave-particle phase-locking between the downward-chirping branch and resonant trapped fast ions, a key process responsible for their outward transport. Finally, systematic parameter scans further establish the dependence of the mode stability on fast-ion parameters.