Understanding the RMP and density pump-out physics from a coupled gyrokinetic-MHD simulation*

Density pump-out caused by external resonant magnetic perturbations (RMP) is studied in a model DIII-D discharge with advanced coupled gyrokinetic-MHD simulation. RMP has been accepted into the ITER design as the primary control tool to suppress edge localized modes (ELMs). Strong RMPs, however, often reduce edge particle confinement (pump-out), which degrades fusion efficiency. In our advanced model, the perturbed plasma equilibrium is calculated with the M3D-C1 code. This equilibrium (including the RMP) is coupled into the edge gyrokinetic XGC suite of codes, which calculate neoclassical and turbulent transport, background plasma and ExB profile evolution including neutral particle physics and X-point orbit loss. In the zero-turbulence limit, we find a significant increase of (neoclassical) radial particle fluxes to levels similar to experimental observations. Edge turbulence intensity rises up to 50% due to the RMPs, mostly from the weakening of the ExB shearing rate, which  is not enough to explain the density pump-out without the increase of neoclassical fluxes.