Liu Yi-Hsin, Hesse M, Guo F, Li H, Nakamura T K M
Dartmouth College, Hanover, New Hampshire 03750, USA.
University of Bergen, Bergen, Norway.
Phys Plasmas. 2018;25(8). doi: 10.1063/1.5042539. Epub 2018 Aug 2.
We demonstrate that the dragging of the magnetic field by the super-Alfvénic shear flows out of the reconnection plane can strongly localize the reconnection x-line in collisionless pair plasmas, reversing the current direction at the x-line. Reconnection with this new morphology, which is impossible in resistive-magnetohydrodynamics, is enabled by the particle inertia. Surprisingly, the quasi-steady reconnection rate remains of order 0.1 even though the aspect ratio of the local x-line geometry is larger than unity, which completely excludes the role of tearing physics. We explain this by examining the transport of the reconnected magnetic flux and the opening angle ma de by the upstream magnetic field, concluding that the reconnection rate is still limited by the constraint imposed at the inflow region. Based on these findings, we propose that this often observed fast rate value of order 0.1 itself, in general, is an upper bound value determined by the upstream constraint, independent of the localization mechanism and dissipation therein.
我们证明，超阿尔文剪切流将磁场拖出重联平面，可在无碰撞粒子对等离子体中使重联x线强烈局域化，同时反转x线处的电流方向。这种具有新形态的重联在电阻磁流体动力学中是不可能的，它是由粒子惯性实现的。令人惊讶的是，尽管局部x线几何形状的纵横比大于1，但准稳态重联率仍保持在0.1左右，这完全排除了撕裂物理机制的作用。我们通过研究重联磁通量的输运以及上游磁场形成的张角对此进行了解释，得出重联率仍受流入区域所施加约束限制的结论。基于这些发现，我们提出，通常观测到的约为0.1的这个快速率值，一般而言是由上游约束所确定的上限值，与其中的局域化机制和耗散无关。
