Dependency of Tearing Mode Stability on Current and Pressure Profiles in DIII-D Hybrid Discharges*

Understanding the physics of the onset and evolution of tearing modes (TMs) in tokamak plasmas is important for high-$\beta$ steady-state operation. Based on DIII-D steady-state hybrid experiments with accurate equilibrium reconstruction and well-measured plasma profiles, the 2/1 tearing mode can be more stable with increasing local current and pressure gradient at rational surface and with lower pressure peaking and plasma inductance. The tearing stability index $\Delta$', estimated by the Rutherford equation with experimental mode growth rate was validated against $\Delta$' calculated by linear eigenvalue solver (PEST3); preliminary comprehensive MHD modeling by NIMROD reproduced the TM onset reasonably well. We present a novel integrated modeling for the purpose of predicting TM onset in experiment by combining a model equilibrium reconstruction using IPS/FASTRAN, linear stability $\Delta$' calculation using PEST3, and fitting formula for critical $\Delta$' from NIMROD.