高磁雷诺数下剪切流对双撕裂模中二级磁岛的影响

doi:10.19596/j.cnki.1001-246x.8235

摘要/Abstract

摘要：

在高磁雷诺数下，当双撕裂模发展进入快速磁场重联阶段时，会发生二级磁岛不稳定性，加剧磁场能量的释放。本文基于扰动形式的守恒磁流体方程组发展高精度的数值模拟程序，在平板位形下研究反对称位形剪切流对双撕裂模中二级磁岛的影响。结果表明：随着剪切流强度和剪切梯度的增加，二级磁岛的数目以及电流片横纵比变小。此外，较强的极向剪切流能够抑制二级磁岛不稳定性的发生。

关键词: 二级磁岛, 剪切流, 高磁雷诺数, 守恒磁流体方程

Abstract:

At high magnetic Reynolds numbers, as double tearing modes develop into rapid magnetic reconnection phase secondary magnetic island instability occurs, which intensifies the release of magnetic field energy. We developed a high-precision numerical simulation program based on perturbed conservative MHD equation. Effect of antisymmetric shear flow on second-order magnetic islands in double tearing modes was studied in a plane configuration. It shows that the number of secondary magnetic islands and current-sheet aspect ratio both decrease with the increase of shear flow velocity and gradient of shear flow velocity. In addition, a strong polar shear flow inhibits the occurrence of secondary magnetic island instability.

Key words: secondary magnetic island, shear flow, high magnetic Reynolds number, conserved MHD equation

中图分类号:

O534⁺.2

谭耀. 高磁雷诺数下剪切流对双撕裂模中二级磁岛的影响[J]. 计算物理, 2021, 38(3): 343-351.

Yao TAN. Effect of Shear Flow on Secondary Magnetic Islands in DTM at High Magnetic Reynolds Numbers[J]. Chinese Journal of Computational Physics, 2021, 38(3): 343-351.

图/表 9

图1 动能随时间变化

Fig.1 Time evolution of logarithmic kinetic energy

图2 不同时刻的磁通

Fig.2 Magnetic flux at different times

图3 快速磁场重联阶段(a)电流密度和(b)等离子体速度流(t=46)

Fig.3 (a) Current density and (b) streamlines of plasma velocity (t= 46)

图4 二级磁岛开始形成时(a)电流密度和(b)等离子体速度流(t= 48)

Fig.4 (a) Current density and (b) streamlines of plasma velocity (t= 48) at beginning of the secondary magnetic island formation

图5 二级磁岛充分发展后(a)电流密度和(b)等离子体速度流(t=50)

Fig.5 (a) Current density and (b) streamlines of plasma velocity (t=50) of a fully developed secondary magnetic island

图6 平衡磁场和平衡流位形

Fig.6 Profiles of equilibrium magnetic field and shear flow

图7 不同剪切流位形下，二级磁岛数目和电流片横纵比随剪切流大小的变化

Fig.7 Numbers of secondary island and current-sheet aspect ratios for different shear flow profiles

图8 二级磁岛充分发展后的磁通与流场

Fig.8 Magnetic flux and plasma velocity streamlines of a fully developed secondary magnetic island

图9 不同剪切流下二级磁岛充分发展后的磁通

Fig.9 Magnetic flux of a fully developed secondary magnetic island under different shear flow

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