Linear MHD stability of 3D equilibrium formed after application of resonant magnetic perturbations

The three-dimensional magnetohydrodynamic code JOREK was utilized to perform a linear study on the HL-2A device. The primary objective of this investigation is to gain insight into how the Resonant Magnetic Perturbation (RMP) influences plasma equilibrium and, consequently, the behavior of the Edge Localized Modes (ELMs). A scan of the n = 1 (n is the toroidal mode number) RMP coil current from 1 to 4.9 kAt reveals a mode transition from n = 4 to n = 3 for the dominant toroidal mode number, after the RMP field exceeds a certain threshold. By comparing the changes in the electron density expansion diagrams at specified magnetic surface locations before and after the transition, it is found that the n = 1 periodic structure resulting from the application of RMP forms an n = 3 mode structure through mode linear coupling with natural ELMs (with the dominant mode number n = 4). This is a key reason for the change in the dominant mode number.