# Non-linear modeling of the threshold between ELM mitigation and ELM suppression by Resonant Magnetic Perturbations in ASDEX Upgrade

## TL;DR

This paper models the complex interaction between ELMs and RMPs in tokamak plasmas, revealing how RMP amplitude influences the transition from mitigation to suppression through mode coupling and edge mode saturation.

## Contribution

It introduces a non-linear magnetohydrodynamic model that captures the bifurcation between ELM mitigation and suppression based on RMP amplitude and mode coupling effects.

## Key findings

- Optimal ELM control occurs with enhanced RMP penetration.
- ELM suppression involves mode locking and flow braking.
- Transition from mitigation to suppression is driven by RMP amplitude increase.

## Abstract

The interaction between Edge Localized Modes (ELMs) and Resonant Magnetic Perturbations (RMPs) is modeled with the magnetohydrodynamic code JOREK using experimental parameters from ASDEX Upgrade discharges. The ELM mitigation or suppression is optimal when the amplification of both tearing and peeling-kink responses result in a better RMP penetration. The ELM mitigation or suppression is not only due to the reduction of the pressure gradient, but predominantly arises from the toroidal coupling between the ELMs and the RMP-induced mode at the plasma edge, forcing the edge modes to saturate at a low level. The bifurcation from ELM mitigation to ELM suppression is observed when the RMP amplitude is increased. ELM mitigation is characterized by rotating modes at the edge, while the mode locking to RMPs is induced by the resonant braking of the electron perpendicular flow in the ELM suppression regime.