Anisotropic viscous dissipation in compressible magnetic X-points
Anisotropic viscous dissipation in compressible magnetic X-points
复制标题
可压缩磁 X 点中的各向异性粘性耗散
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
I. Craig
中科院分区：
文献类型：
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作者：
I. Craig
上下文。研究了线系磁x点的粘阻阻尼。目标。目标是确定是否快速，阿尔芬能量耗散是可能的x点扰动由等离子体电阻率和非各向同性粘度阻尼。方法。通过求解二维半线性化的可压缩MHD方程，探讨了x点对平面和轴向扰动的响应。结果。结果表明，在弱阻等离子体中，受各向异性黏性阻尼的非再连接平面扰动下，快速耗散是可能的。虽然当粘性效应占主导地位时，改变初始x点拓扑的扰动在长时间内衰减缓慢，但在阿尔芬尼克时间尺度上存在一个初始阶段，其中很大一部分扰动能量被去除。然而，非压缩轴向场扰动的衰减是通过不同的机制发生的，这在形式上总是缓慢的（即依赖于小的粘性和阻力阻尼系数）。结论。计算表明，在压缩x点扰动下，日冕等离子体中的快速粘阻能量释放是可能的。这一结果可能对理解日冕活动区的快速能量释放具有重要意义。
Context. Visco-resistive damping in line-tied magnetic X-points is examined. Aims. The goal is to determine whether fast, Alfvenic energy dissipation is possible for X-point disturbances damped by the plasma resistivity and non-isotropic viscosity. Methods. The response of X-points to planar and axial perturbations is explored numerically by solving the linearized compressible MHD equations in two and a half dimensions. Results. It is demonstrated that fast dissipation is possible in the case of non-reconnective planar disturbances damped by anisotropic viscosity in weakly resistive plasmas. Although perturbations which change the initial X-point topology decay slowly at large times when viscous effects are dominant, there is an initial phase in which a significant fraction of the disturbance energy is removed on an Alfvenic timescale. The decay of incompressive axial field disturbances occurs by a different mechanism, however, that is always formally slow (i.e. dependent on the small viscous and resistive damping coefficients). Conclusions. Computations suggest that fast, visco-resistive energy release in coronal plasmas is possible for compressive X-point disturbances. This result could have important implications for understanding rapid energy release in coronal active regions.