Resonant layer responses to 3D magnetic perturbations across linear, two-fluid, drift-MHD regimes*

3D magnetic perturbations arising in a tokamak can induce complex plasma responses near the

resonant surface. In this region, the plasma will no longer adhere to ideal MHD and will instead

demand the reconnection of magnetic field lines which can grow and significantly alter the

plasma profile. This resonant layer response can be characterized in a linear regime by a single

parameter called the inner-layer Δ. Here we apply a two-fluid drift-MHD model to identify the

scaling of Δ in various asymptotic regimes, and confirm the predictions using a numerical

method based on the Riccati transformation [1]. In particular, the Δ variations across the strong

viscous or recently proposed diffusive [2] regimes have been further investigated and compared

with additional analytic solutions. These Δ calculations have also been used to predict the field

penetration threshold by matching to outer-layer response solutions in general perturbed equilibrium

code (GPEC), and validate the predictions over the tokamak error field database.

[1] J.K. Park, accepted in Phys. Plasmas (2022)

[2] R. Fitzpatrick, Phys. Plasmas 29, 032507 (2022)