Development of coupled extended-MHD and gyrokinetic simulation capabilities for edge stability in spherical tokamaks

We present progress on coupling the extended-MHD code M3D-C1 with the gyrokinetic code XGC, to enable the use of gyrokinetic diffusion profiles in extended-MHD simulations of ELM thresholds. In order to increase confidence in the simulation predictions, we also benchmark the extended-MHD codes NIMROD, M3D-C1 and MARS for simulations of peeling-ballooning (PB) modes in ELMy and non-ELMing H-mode discharges on NSTX. Moving towards higher fidelity predictions, another benchmark for low-n core modes is presented between XGC and M3D-C1. For the purpose of code verification and to ensure ELM-stability results are of high fidelity, it is important to benchmark these codes for edge stability simulations, as the edge region can be very challenging for numerical simulations. The first set of benchmarks is performed at different resistivity values including the ideal-MHD limit, and with and without finite-Larmor radius effects. Our benchmark comprises linear and nonlinear simulations. We find good agreement in terms of the linear growth rates between the initial value extended-MHD codes. The nonlinear simulations are ongoing, but so far we find similar results.