Large scale instabilities in two-dimensional magnetohydrodynamics
Large scale instabilities in two-dimensional magnetohydrodynamics
复制标题
二维磁流体动力学中的大规模不稳定性
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
Prandi
中科院分区：
文献类型：
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作者：
Boffetta;Celani;Prandi
在二维磁流体动力学中，分析了剪切磁场的稳定性。使用多尺度分析，它表明，在足够大的雷诺数的基本状态描述一个不动的流体和分层的磁场，变得不稳定的大尺度扰动。在临界点附近导出了涡粘性和涡电阻率的精确表达式。在这种轻微不稳定的情况下，扰动增长的非线性阶段服从Cahn-Hilliard-like动力学，其特征在于磁岛的合并导致最终的新的平衡状态。高分辨率数值模拟定量地证实了多尺度分析的预测。
The stability of a sheared magnetic field is analyzed in two-dimensional magnetohydrodynamics with resistive and viscous dissipation. Using a multiple-scale analysis, it is shown that at large enough Reynolds numbers the basic state describing a motionless fluid and a layered magnetic field, becomes unstable with respect to large scale perturbations. The exact expressions for eddy-viscosity and eddy-resistivity are derived in the nearby of the critical point where the instability sets in. In this marginally unstable case the nonlinear phase of perturbation growth obeys to a Cahn-Hilliard-like dynamics characterized by coalescence of magnetic islands leading to a final new equilibrium state. High resolution numerical simulations confirm quantitatively the predictions of multiscale analysis.