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- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> </mml:math> simulations identify unstable energetic particle modes (EPMs) with toroidal mode numbers <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:math> , along with an <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:math> 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.