Description
We present a novel model that calculates the extended-MHD peeling-ballooning (PB) stability threshold as a function of pedestal height and width, providing a higher-fidelity constraint for the onset of edge-localized modes (ELMs). This is crucial in spherical tokamaks (STs) where resistive PB modes have been observed, but can also be relevant for conventional aspect ratio devices such as JET-ILW. Existing pedestal models like EPED and Europed rely on ideal-MHD stability and simplified gyrokinetic constraints, but effects beyond ideal-MHD - such as resistivity and finite-Larmor-radius effects – can be included in our new model and could play an important role in larger STs such as STAR and STEP. We developed a tool that generates equilibrium variations using the TokaMaker equilibrium code, allowing systematic and physically meaningful variation of pedestal parameters based on experimental kinetic EFITs and model equilibria. The tool is interfaced with the extended-MHD initial value code M3D-C1 to compute PB thresholds as a function of pedestal height and width for NSTX and MAST-U. Significant differences are found between extended- and ideal-MHD stability limits, highlighting the importance of non-ideal effects. This new framework, which can include neoclassical corrections to resistivity and finite-Larmor-radius stabilization, enables a more realistic determination of pedestal stability constraints in regimes where ideal-MHD models are insufficient.