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

Nuclear Fushion

article

Hanzheng Li¹  Yasushi Todo¹  Hao Wang²  Jialei Wang²  Malik Idouakass² 

[1] The University of Tokyo;National Institute for Fusion Science, National Institutes of Natural Sciences

关键词: scrape-off layer;    parallel transport;    non-local;    kinetic modelling;    sheath;   

DOI  :  10.1088/1741-4326/acdeff

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

We have investigated the waveform distortion of energetic particle driven off-axis fishbone mode (OFM) in tokamak plasmas with kinetic magnetohydrodynamic (MHD) hybrid simulations. We extended our previous simulations (Liet al2022Nucl. Fusion62026013) by considering higher- nharmonics in the MHD fluid, wherenis toroidal mode number. The waveform distortion is successfully reproduced in the simulation for both magnetic fluctuations and temperature fluctuations. It is clarified that the waveform distortion arises from the superposition of then  = 2 harmonics on the fundamentaln  = 1 harmonics of OFM, where then  = 2 harmonics are generated by the MHD nonlinearity from then  = 1 OFM. Two types of waveform distortion can occur depending on the phase relationship between then  = 1 andn  = 2 harmonics and the relative amplitude of then  = 2 harmonics to then  = 1 harmonics. Lissajous curve analyses indicate that the wave couplings between then  = 1 andn  = 2 harmonics with phase-lock {sim}piand {sim}0lead to 'rising distortion' and 'falling distortion', respectively. The two types of waveform distortion can be attributed to the strong shearing profile of radial MHD velocity withn  = 2 around theq  = 2 magnetic flux surface. The dependence of waveform distortion on viscosity is investigated. It is found that the viscosity which is needed to reproduce the waveform distortion is larger than that in the experiment.

【 授权许可】

Unknown