Magnetic reconnection at three-dimensional null points
Magnetic reconnection at three-dimensional null points
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DOI：
10.1098/rsta.1996.0136
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发表时间：
1996-12
期刊：
影响因子：
--
通讯作者：
E. Priest;Viacheslav Titov
中科院分区：
文献类型：
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作者：
E. Priest;Viacheslav Titov
三维孤立零点的骨架由一条‘脊曲线’和一个‘扇面’组成。两条孤立的磁力线沿着脊柱从两个方向接近(或远离)零点，而连续的磁力线从(或接近)风扇表面平面上的零点后退。两束场线接近脊椎周围的零点(每个方向一束)，并在风扇附近展开。考虑在这样的零点处稳定重新连接的运动学，这取决于封闭零点的表面上施加的边界条件的性质，特别是在其轴沿脊线的圆柱面上。发现了三种类型的重联。在脊椎重新连接中，连续的脚点运动被施加在弯曲的圆柱面上，穿过风扇并沿脊椎驱动单一的喷射流。在“风扇重联”中，规定了气缸两端的连续脚点运动，穿过脊椎，在风扇上驱动一个单独的旋转运动。证明了一个反重联定理，该定理指出，在高亚Alfvenic流和均匀磁扩散率的无粘等离子体中，三维稳定的MHD重联是不可能的，等离子体流穿过脊柱或风扇。这其中的一个含义是，重新连接往往是一种内在的非线性现象。发展了一种慢速稳定重联的线性理论，该理论清楚地证明了脊柱重联中脊柱奇异性的本质。最后，通过分析实例讨论了含有两个零点的复杂构型中分离器重联的性质。
The skeleton of an isolated null point in three dimensions consists of a ‘spine curve’ and a ‘fan surface’. Two isolated magnetic field lines approach (or recede from) the null point from both directions along the spine, and a continuum of field lines recedes from (or approaches) the null in the plane of the fan surface. Two bundles of field lines approach the null point around the spine (one from each direction) and spread out near the fan. The kinematics of steady reconnection at such a null point is considered, depending on the nature of the imposed boundary conditions on the surface that encloses the null, in particular on a cylindrical surface with its axis along the spine. Three kinds of reconnection are discovered. In ‘spine reconnection’ continuous footpoint motions are imposed on the curved cylindrical surface, crossing the fan and driving singular jetting flow along the spine. In ‘fan reconnection’ continuous footpoint motions are prescribed on the ends of the cylinder, crossing the spine and driving a singular swirling motion at the fan. An antireconnection theorem is proved, which states that steady MHD reconnection in three dimensions with plasma flow across the spine or fan is impossible in an inviscid plasma with a highly subAlfvenic flow and uniform magnetic diffusivity. One implication of this is that reconnection tends to be an inherently nonlinear phenomenon. A linear theory for slow steady reconnection is developed which demonstrates explicitly the nature of the spine singularity in spine reconnection. Finally, the properties of separator reconnection’ in complex configurations containing two null points are discussed by means of analytical examples.