Plasma flow evolution in response to resonant magnetic perturbation in a tokamak

TL;DR

This study investigates how resonant magnetic perturbations influence plasma flow evolution in tokamaks, comparing full resistive MHD simulations with extended nonlinear response theories, highlighting the importance of the slip condition in plasma response modeling.

Contribution

The paper extends nonlinear plasma response theory to include a free-slip condition and validates it against detailed MHD simulations for RMP-driven flow evolution.

Findings

Extended theory with free-slip condition matches simulation results across resistive regimes.

Conventional no-slip theory diverges from simulations as resistivity decreases.

Good agreement achieved between extended theory and full MHD simulations.

Abstract

Externally applied non-axisymmetric magnetic fields such as error field and resonant magnetic perturbation (RMP) are known to influence the plasma momentum transport and flow evolution through plasma response in a tokamak, whereas the evolution of plasma response itself strongly depends on the plasma flow as well. The nonlinear interaction between the two have been captured in the conventional error field theory with a ``no-slip'' condition, which has been recently extended to allow the ``free-slip'' condition. For comparison with simulations, we solve for the nonlinear plasma response and flow evolution driven by a single-helicity RMP in a tokamak, using the full resistive MHD model in the initial-value code NIMROD. Time evolution of the parallel (to ${\mathbf k}$) flow or ``slip frequency'' profile and its asymptotic steady state obtained from the NIMROD simulations are compared with both conventional and extended nonlinear response theories. Here ${\mathbf k}$ is the wave vector of the propagating island. Good agreement with the extended theory with ``free-slip'' condition has been achieved for the parallel flow profile evolution in response to RMP in all resistive regimes, whereas the difference from the conventional theory with the ``no-slip'' condition tends to diminish as the plasma resistivity approaches zero.