Nonlinear evolution of ion temperature gradient mode in non-axisymmetric temperature profiles along magnetic islands*

Resonant magnetic field perturbations (RMPs) are promising candidates for controlling edge localized modes in tokamaks. Plasma transport models assuming axisymmetric nested flux surfaces may not be valid in the presence of RMP-caused magnetic islands (MIs). The gyrokinetic particle-in-cell code, XGC-S, can handle non-axisymmetric geometries without magnetic coordinates and serves as a powerful tool to address this issue. We focus on the effects of background temperature profiles modified by MIs on the ion temperature gradient (ITG) mode. A set of pseudo flux labels describing the flux structures inside and outside the MIs is defined by field line tracing. These flux labels can model the temperature profiles modified by field-aligned plasma dynamics. Using XGC-S, we perform direct delta-f simulations of the ITG mode with a relaxed temperature profile inside the MIs. The temperature profile has significant effects even if the RMP component has only a small impact on ion dynamics. While the linear growth rate increases along a steep temperature gradient region around the MIs, the electric field and velocity shear generated there effectively decrease the growth rate in the non-linear simulation. Despite these stabilization effects, the modified temperature profile drives turbulence, maintaining a relatively large turbulence level after the saturation phase.