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 in ASDEX Upgrade. 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 500 μs. 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.

中文翻译：

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ASDEX 升级中 I 型边缘局部模式循环的非线性扩展 MHD 模拟及其底层触发机制

通过首次在 ASDEX 升级中对重复 I 型 ELM 进行非线性磁流体动力学模拟，确定了导致聚变等离子体中边缘局部模式 (ELM) 爆发的触发机制。简而言之，在 ELM 崩溃之前，不稳定和稳定项在不同的时间尺度上受到越来越多的遍历磁场的影响，该磁场是由轴对称背景等离子体和不断增长的非轴对称扰动之间的非线性相互作用引起的。时间尺度的分离促进了持续 500 微秒的 ELM 崩溃的爆炸性增长，即比指数增长更快。模拟 ELM 崩溃的持续时间和大小与 ASDEX 升级中的 I 型 ELM 相比质量很好。正如 I 型 ELM 所预期的那样，获得了模拟中的加热功率和 ELM 重复频率之间的正比关系。这里介绍的模拟是朝着 ELM 预测建模和 ITER 和其他未来托卡马克缓解技术评估迈出的重要一步。