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首页> 外文期刊>Plasma and Fusion Research >Magnetic Island Formation by External Cyclic Perturbation in Rotating and Non-rotating Plasmas
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Magnetic Island Formation by External Cyclic Perturbation in Rotating and Non-rotating Plasmas

机译：旋转和非旋转等离子体中外部循环扰动引起的磁岛形成

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摘要

Effects of a non-monotonically evolving external perturbation on a plasma, that is stable against tearing modes, are numerically investigated. It is found that for a magnetic island driven by an external single-cycle magnetic perturbation, the time constants during the phases of growth and decay are different. This difference in time constants causes a finite magnetic island to form even after the external perturbation is removed. Therefore, the saturation width of a magnetic island driven by a successive applications of an external single-cycle perturbation becomes larger than the maximum magnetic island width driven by a single application of that. For a rotating plasma, the background rotation is damped as the magnetic island grows due to an external perturbation [R. Fitzpatrick, Phys. Plasmas 5, 3325(1998)]. Therefore, for a rotating plasma, the driven magnetic island can enter an explosive growth stage due to successive applications of a single-cycle perturbation even with amplitude smaller than the critical value for the onset of the rapid growth in the case of a monotonically increasing or step-function type external perturbation. These features are important in explaining the explosive growth of magnetic islands and the onset of neoclassical tearing mode due to non-monotonically growing MHD phenomena such as sawtooth, fishbones and ELM.
机译：数值研究了非单调演变的外部扰动对等离子体的影响，该扰动对撕裂模式稳定。发现对于由外部单周期磁扰动驱动的磁岛，在生长和衰减阶段的时间常数是不同的。时间常数的这种差异即使在消除了外部扰动后仍会形成一个有限的磁岛。因此，由外部单周期扰动的连续施加驱动的磁岛的饱和宽度变得大于由其单次施加驱动的最大磁岛宽度。对于旋转的等离子体，由于外部扰动，背景旋转会随着磁岛的增长而衰减[R.菲茨帕特里克，物理学。 Plasmas 5，3325（1998）]。因此，对于旋转的等离子体，由于单周期扰动的连续施加，从动磁岛即使在单调增大或增大的情况下，即使振幅小于开始快速增长的临界值，也可以进入爆炸性增长阶段。阶跃型外部扰动。这些特征对于解释磁岛的爆炸性增长以及由于非单调增长的MHD现象（如锯齿，鱼骨和ELM）而导致的新古典撕裂模式的出现非常重要。

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