Pyakurel P S, Shay M A, Drake J F, Phan T D, Cassak P A, Verniero J L
Space Sciences Laboratory, University of California, Berkeley, California 94720, USA.
University of Delaware, Newark, Delaware 19716, USA.
Phys Rev Lett. 2021 Oct 8;127(15):155101. doi: 10.1103/PhysRevLett.127.155101.
Observations in Earth's turbulent magnetosheath downstream of a quasiparallel bow shock reveal a prevalence of electron-scale current sheets favorable for electron-only reconnection where ions are not coupled to the reconnecting magnetic fields. In small-scale turbulence, magnetic structures associated with intense current sheets are limited in all dimensions. And since the coupling of ions are constrained by a minimum length scale, the dynamics of electron reconnection is likely to be 3D. Here, both 2D and 3D kinetic particle-in-cell simulations are used to investigate electron-only reconnection, focusing on the reconnection rate and associated electron flows. A new form of 3D electron-only reconnection spontaneously develops where the magnetic X-line is localized in the out-of-plane (z) direction. The consequence is an enhancement of the reconnection rate compared with two dimensions, which results from differential mass flux out of the diffusion region along z, enabling a faster inflow velocity and thus a larger reconnection rate. This outflow along z is due to the magnetic tension force in z just as the conventional exhaust tension force, allowing particles to leave the diffusion region efficiently along z unlike the 2D configuration.
在准平行弓形激波下游的地球湍动磁鞘层中的观测结果表明，存在有利于仅电子重联的电子尺度电流片，在这种情况下离子未与重联磁场耦合。在小尺度湍动中，与强电流片相关的磁结构在所有维度上都受到限制。并且由于离子的耦合受最小长度尺度的约束，电子重联的动力学可能是三维的。在此，二维和三维动力学粒子模拟被用于研究仅电子重联，重点关注重联率和相关的电子流。一种新形式的仅电子三维重联自发形成，其中磁X线在面外（z）方向上局部化。其结果是与二维相比重联率有所提高，这是由于沿z方向从扩散区域流出的质量通量差异导致的，使得流入速度更快，从而重联率更大。这种沿z方向的流出是由于z方向上的磁张力，就如同传统的排气张力一样，与二维构型不同，它使得粒子能够有效地沿z方向离开扩散区域。
