NUMERICAL EXPERIMENTS ON FINE STRUCTURE WITHIN RECONNECTING CURRENT SHEETS IN SOLAR FLARES
NUMERICAL EXPERIMENTS ON FINE STRUCTURE WITHIN RECONNECTING CURRENT SHEETS IN SOLAR FLARES
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DOI：
10.1088/0004-637x/737/1/14
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发表时间：
2011-08
期刊：
影响因子：
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通讯作者：
Chengcai Shen;Jun Lin;N. Murphy
中科院分区：
文献类型：
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作者：
Chengcai Shen;Jun Lin;N. Murphy
我们进行电阻磁流体动力学模拟，研究在太阳爆发过程中形成的电流片的内部结构。模拟开始于一个垂直的电流片在机械和热平衡，分离两个区域的磁场与相反的极性，这是线绑在代表光球的下边界。由于最初施加的扰动，重新连接逐渐开始，但当等离子体团形成并在电流片内产生小尺度结构时，重新连接变得更快。这些结构包括磁岛或沿沿着片在两个方向上流动的等离子体斑点，以及相邻岛对之间的X点。在这些X点中，存在重连率达到最大值的主要X点。在重联流出分叉处，出现了流体滞止点（S点）。S点和主X点（PX点）在空间上并不共位，尽管它们彼此非常接近。它们的相对位置随着重联的进展而交替变化，并决定了各个磁岛的运动方向。如果S点位于PX点上方，新形成的岛屿向上移动，如果S点位于PX点下方，则向下移动。磁岛的合并，偶尔观察到在同一方向移动的岛屿之间。观察到重新连接的等离子体流比附近的斑点移动得更快。
We perform resistive magnetohydrodynamic simulations to study the internal structure of current sheets that form during solar eruptions. The simulations start with a vertical current sheet in mechanical and thermal equilibrium that separates two regions of the magnetic field with opposite polarity which are line-tied at the lower boundary representing the photosphere. Reconnection commences gradually due to an initially imposed perturbation, but becomes faster when plasmoids form and produce small-scale structures inside the current sheet. These structures include magnetic islands or plasma blobs flowing in both directions along the sheet, and X-points between pairs of adjacent islands. Among these X-points, a principal one exists at which the reconnection rate reaches maximum. A fluid stagnation point (S-point) in the sheet appeared where the reconnection outflow bifurcates. The S-point and the principal X-point (PX-point) are not co-located in space though they are very close to one another. Their relative positions alternate as reconnection progresses and determine the direction of motion of individual magnetic islands. Newly formed islands move upward if the S-point is located above the PX-point, and downward if the S-point is below the PX-point. Merging of magnetic islands was observed occasionally between islands moving in the same direction. Reconnected plasma flow was observed to move faster than blobs nearby.