Characteristics of turbulence spreading and zonal flow near magnetic island in electrostatic gyrokinetic simulations*

We present characteristics of turbulence spreading and zonal flow near magnetic island in electrostatic simulations of a gyro-kinetic code, XGC1. This work was motivated by recent ECEI measurements in dedicated KSTAR experiment employing resonant magnetic field perturbation(RMP). From the experiment, it was found that magnetic island induced by RMP can impact fluctuations and flows, and consequently electron thermal transport around the island[1]. A subsequent simulation study showed that 3D RMP field can enhance equilibrium ExB flow strong enough to suppress ambient micro-instabilities[2]. In this talk, we present more comprehensive nonlinear simulations with all relevant neoclassical and turbulence physics in the KSTAR experimental condition. In the simulations, we explore turbulence evolution around and inside (2,1) magnetic island. Unlike linear analysis results, fluctuation penetrates the strong ExB shearing layer around the island and the electron temperature profile inside has a finite gradient. We also investigate how flow evolution around the island affect ambient transport.

[1] M.J. Choi et al., NF 57, 126058 (2017)

[2] Jae-Min Kwon et al., PoP 25, 052506 (2018)