Gyrokinetic Simulations with External Resonant Magnetic Perturbations: Island Torque and Nonambipolar Transport with Rotation

Static external resonant magnetic perturbations (RMPs) have been added to the $\delta f$ gyrokinetic code GYRO. This allows nonlinear gyrokinetic simulations of the nonambipolar radial current flow $j_r$ and the corresponding plasma torque (density) $R[j_rB_\theta/c]$, induced by islands that break the toroidal symmetry of a tokamak. This extends previous GYRO simulations for the transport of toroidal angular momentum (TAM) [1,2]. The focus is on full torus radial slice electrostatic simulations of induced q=m/n=6/3 islands with widths 5\% of the minor radius. The island torque scales with the radial electric field $E_r$ the island width $w$, and the intensity $I$ of the high-n micro-turbulence, as $wE_rI^{1/2}$. The net island torque is null at zero $E_r$ rather than at zero toroidal rotation. This means that there is a small co-directed magnetic acceleration to the small diamagnetic co-rotation corresponding to the zero $E_r$ which can be called the residual stress [2] from an externally induced island. Finite-beta GYRO simulations of a core radial slice demonstrate island unlocking and the RMP screening.\par \vskip6pt\noindent [1]~R.E. Waltz, et al., Phys. Plasmas {\bf 14}, 122507 (2007).\par\noindent [2]~R.E. Waltz, et al., Phys. Plasmas {\bf 18}, 042504 (2011).