NIMROD Simulations of Forced Magnetic Reconnection in DIII-D Limited L-mode Plasmas

This work focuses on physics of mode penetration in limited, L-mode plasmas in the DIII-D tokamak using the extended-magnetohydrodynamic code NIMROD. Simulations are initialized with results from kinetic-EFIT for magnetic profiles, OMFIT for thermal and rotation profiles, and TRIP3D for vacuum magnetic perturbation fields. When the resonant magnetic perturbation (RMP) magnitude is increased in a rotating plasma, the electromagnetic force imparted by the RMP on the flow-screened island can decrease the local flow, causing the external field to rapidly penetrate. Furthermore, the plasma response at a rational surface depends on dissipation and rotation, setting the threshold RMP for mode penetration. To elucidate the plasma response due to applied RMPs, we present parametric analyses of linear simulations scaling rotation and dissipation. Numerical results are compared to conventional analytical treatments including tearing and twisting plasma responses. Intuition gained from linear results will be utilized in a nonlinear study of mode penetration with tentative comparisons to DIII-D results.