MHD stability in X-point geometry: simulation of ELMs
MHD stability in X-point geometry: simulation of ELMs
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DOI：
10.1088/0029-5515/47/7/016
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发表时间：
2007-06
期刊：
影响因子：
3.3
通讯作者：
G. Huysmans;O. Czarny
中科院分区：
文献类型：
--
作者：
G. Huysmans;O. Czarny
一个非线性MHD代码，名为JOREK，正在开发中的目的是研究的MHD不稳定性的非线性演化被认为是负责边缘局域模式（ELMs）：外部扭结（剥离）和介质n气球模式。考虑了完整的环形X点几何形状，包括分界线，开放和封闭的场线。的分界线的影响分析表明，一个强大的稳定的理想和电阻MHD外部扭结/剥离模式。一种不稳定性在X点的存在下保持不稳定，其特征在于撕裂和剥离模式的组合。所谓的剥离-撕裂模式对边q的依赖性要弱得多。非线性的n = 1剥离撕裂模式饱和，在一个恒定的振幅产生一个大部分扭结状扰动的边界与岛状结构接近的X点。中氮气球模式的非线性演化显示了密度细丝的形成。密度细丝从主等离子体中剪切下来，由麦克斯韦应力引起的n = 0非线性流动。气球模式的振幅受此n = 0流的限制，并且多个（在时间上）密度细丝可以发展成使等离子体低于稳定性边界。
A non-linear MHD code, named JOREK, is under development with the aim of studying the non-linear evolution of the MHD instabilities thought to be responsible for edge localized modes (ELMs): external kink (peeling) and medium-n ballooning modes. The full toroidal X-point geometry is taken into account including the separatrix, open and closed field lines. Analysis of the influence of the separatrix shows a strong stabilization of the ideal and resistive MHD external kink/peeling modes. One instability remains unstable in the presence of the X-point, characterized by a combination of a tearing and a peeling mode. The so-called peeling–tearing mode shows a much weaker dependence on the edge q. Non-linearly the n = 1 peeling–tearing mode saturates at a constant amplitude yielding a mostly kink-like perturbation of the boundary with an island-like structure close to the X-point. The non-linear evolution of a medium-n ballooning mode shows the formation of density filaments. The density filaments are sheared off from the main plasma by an n = 0 flow non-linearly induced by the Maxwell stress. The amplitude of the ballooning mode is limited by this n = 0 flow and multiple (in time) density filaments can develop to bring the plasma below the stability boundary.