The impact of magnetic islands on microtubulent transport in KSTAR*

Global gyrokinetic simumlations with kinetic electrons are performed to study microturbulence in the presence of magnetic islands with self-generated ExB shear flow around islands. In this work, we use the global gyrokinetic toroidal code GTC with a drift kinetic electron model to simulate microturbulence in the KSTAR tokamak with resonant magnetic perturbation (RMP). Magnetic islands generated by RMP coils are included in the equilibrium which is obtained from M3D-C1 MHD simulations of the discharge #19118. Simulations shows microturbulence is dominated by Ion temperature gradient (ITG) turbulence. Magnetic islands have little effect on linear growth rate, frequency and spectrum of the ITG instability. However, larger transport levels are found in nonlinear simulations near the X points of the island compared to the O points. A vortex flow, an ExB flow around the islands by electrostatic potential with the same periodicity and location as the magnetic island, is nonlinearly generated and regulates the ITG turbulence across the islands.