Thermal ion kinetic effects and Landau damping in fishbone modes

TL;DR

This paper extends kinetic-MHD simulations to include thermal ion effects and Landau damping in fishbone modes, revealing their impact on mode frequency and stability in tokamak plasmas.

Contribution

The authors develop a new coupling scheme in kinetic-MHD simulations that incorporates thermal ion kinetic effects and Landau damping, enhancing the modeling of fishbone instabilities.

Findings

Thermal ion effects increase fishbone mode frequencies for q_min>1.

Landau damping provides additional stabilization of fishbone modes.

Nonlinear simulations show magnetic surface perturbations and energetic particle transport.

Abstract

The kinetic-MHD hybrid simulation approach for macroscopic instabilities in plasmas can be extended to include the kinetic effects of both thermal ions and energetic ions. The new coupling scheme includes synchronization of density and parallel velocity between thermal ions and MHD, in addition to pressure coupling, to ensure the quasineutrality condition and avoid numerical errors. The new approach has been implemented in the kinetic-MHD code M3D-C1-K, and was used to study the thermal ion kinetic effects and Landau damping in fishbone modes in both DIII-D and NSTX. It is found that the thermal ion kinetic effects can cause an increase of the frequencies of the non-resonant $n=1$ fishbone modes driven by energetic particles for $q_\mathrm{min}>1$, and Landau damping can provide additional stabilization effects. A nonlinear simulation for $n=1$ fishbone mode in NSTX is also performed, and the perturbation on magnetic flux surfaces and the transport of energetic particles are calculated.