Waveform distortion of off-axis fishbone instability in the nonlinear magnetohydrodynamic evolution in tokamak plasma

Abstract We have investigated the waveform distortion of energetic particle driven off-axis fishbone mode (OFM) in tokamak plasmas with kinetic magnetohydrodynamic (MHD) hybrid simulations. extended our previous simulations (Li et al 2022 Nucl. Fusion 62 026013) by considering higher-n harmonics MHD fluid, where n is toroidal number. The successfully reproduced simulation for both magnetic fluctuations and temperature fluctuations. It clarified that arises from superposition = 2 on fundamental 1 OFM, are generated nonlinearity OFM. Two types can occur depending phase relationship between relative amplitude to harmonics. Lissajous curve analyses indicate wave couplings phase-lock ∼ π 0 lead “rising distortion” “falling distortion”, respectively. two be attributed strong shearing profile radial velocity around q flux surface. dependence viscosity investigated. found which needed reproduce larger than experiment.