Dynamical investigation of three‐dimensional reconnection in quasi‐separatrix layers in a boundary‐driven magnetic field
Dynamical investigation of three‐dimensional reconnection in quasi‐separatrix layers in a boundary‐driven magnetic field
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边界驱动磁场中准分离层三维重联的动力学研究
DOI：
10.1029/1999ja900398
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发表时间：
2000
影响因子：
--
通讯作者：
K. Galsgaard
中科院分区：
文献类型：
--
作者：
K. Galsgaard
准分离线层是空间中场线连通性的映射变化特别快的区域。这些层被认为是三维磁场中可能存在磁重联的特殊位置。以前的调查是分析性的，并采取了不同的简化假设来调查这个问题。本文用数值方法研究了准分离线层的动力学性质。使用分析研究建议的驱动器强调了磁拓扑，但对其进行了修改以适应采用的边界条件。实验表明，电流确实在数值域中的特定位置积累。电流的大小和位置强烈地依赖于被施加的驱动器的轮廓，并且它们被发现是由驾驶所施加的场线部分的变化产生的。因此，它们是自由磁能在扰动磁场中的表现形式。在磁场停止应力后，发现等离子体压力能够平衡应力磁场的洛伦兹力，并防止电流幅度在电流层中继续增长。在包括磁阻率在内的实验中会产生场线变化。重新连接发生在沿磁场的电场分量较大的位置。磁力线连通性的变化使磁力线上的流动速度仅为当地阿尔芬速度的一小部分。
Quasi-separatrix layers are regions in space where the mapping of field line connectivity changes especially rapidly. These layers have been suggested as special locations in three-dimensional magnetic fields that may host magnetic reconnection. Previous investigations have been analytical and have taken different simplifying assumptions to investigate the problem. This paper takes a numerical approach to investigate the dynamical properties of quasi-separatrix layers. The magnetic topology is stressed using drivers suggested by the analytical investigations but modified to fit the adopted boundary conditions. The experiments show that current does accumulate at specific locations in the numerical domain. The current magnitude and location depend strongly on the profile of the imposed driver, and they are found to be generated by the changes in field line parts imposed by the driving. They are therefore the manifestation of free magnetic energy in the perturbed magnetic field. After the stressing of the field has stopped, it is found that the plasma pressure is able to balance the Lorentz force of the stressed magnetic field and prevent a continued growth of the current amplitude in the current layers. Field-line changes are produced in the experiments that include magnetic resistivity. The reconnection takes place at locations where the electric field component along the magnetic field is large. The changes in field-line connectivity initiate flow velocities across the magnetic field lines at only a small fraction of the local Alfven velocity.