Non-linear extended MHD simulations of type-I edge localised mode cycles in ASDEX Upgrade and their underlying triggering mechanism

• Published in: arXiv.org
• Main Authors: Cathey, Andres, Hoelzl, M, Lackner, K, Huijsmans, G T A, Dunne, M G, Wolfrum, E, Pamela, S J P, Orain, F, Günter, S, the JOREK team, the ASDEX Upgrade Team, the EUROfusion MST1 Team
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 26.10.2020
• Subjects: Computational fluid dynamics; Computer simulation; Crashes; Fluid flow; Magnetohydrodynamic simulation; Physics - Plasma Physics; Plasmas (physics); Prediction models; Simulation; Tokamak devices
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2007.09997

A triggering mechanism responsible for the explosive onset of edge localised modes (ELMs) in fusion plasmas is identified by performing, for the first time, non-linear magnetohydrodynamic simulations of repetitive type-I ELMs. Briefly prior to the ELM crash, destabilising and stabilising terms are affected at different timescales by an increasingly ergodic magnetic field caused by non-linear interactions between the axisymmetric background plasma and growing non-axisymmetric perturbations. The separation of timescales prompts the explosive, i.e. faster than exponential, growth of an ELM crash which lasts \({\sim}\) 500 \({\mu}\)s. The duration and size of the simulated ELM crashes compare qualitatively well with type-I ELMs in ASDEX Upgrade. As expected for type-I ELMs, a direct proportionality between the heating power in the simulations and the ELM repetition frequency is obtained. The simulations presented here are a major step forward towards predictive modelling of ELMs and of the assessment of mitigation techniques in ITER and other future tokamaks.