BOUT++ simulation study of turbulence transport during n = 4 resonant magnetic perturbation induced edge localized mode suppression phase in EAST

The effect of the resonant magnetic perturbation (RMP) on the turbulence transport during the edge localized mode (ELM) suppression phase is investigated by the BOUT++ six-field two-fluid simulations. Based on the edge plasma profiles during the ELM suppression phase in EAST experiment with n = 4 RMP (n is the toroidal mode number), the plasma response field is calculated using CLTx and introduced in the BOUT++ simulation. Compared with the case without RMP, the simulated flux-surface averaged radial particle flux at the position of peak pressure gradient increases to ∼1.5 times for the case with RMP, which is close to the estimated particle flux according to the experimental plasma profiles. It implies that the turbulence transport could have a dominating contribution to the radial transport for maintaining the pedestal density profile during ELM suppression phase after density pump-out, especially when the stochasticity of the magnetic field is not significant in the pedestal region. The increase in the radial particle flux for the case with RMP is due to the significant increase in electric drift flux, which is partly offset by the magnetic flutter flux. The enhancement of the turbulent electric drift flux is mainly due to the enhanced density and electric potential perturbations. The change in the phase difference between them further enhances the contributions of the medium-n modes and suppresses the contribution of the low-n modes. Further complexity–entropy analysis indicates that the turbulence is more stochastic, which could be related to the enhanced mode-mode coupling due to RMP effect.