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

Abstract 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> ( n is the toroidal mode number) RMP coil current from 1 to 4.9 kAt reveals a mode transition from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:math> to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:math> 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> periodic structure resulting from the application of RMP forms an <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:math> mode structure through mode linear coupling with natural ELMs (with the dominant mode number <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>n</mml:mi> <mml:mo>=</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:math> ). This is a key reason for the change in the dominant mode number.