Cozzani G, Khotyaintsev Yu V, Graham D B, Egedal J, André M, Vaivads A, Alexandrova A, Le Contel O, Nakamura R, Fuselier S A, Russell C T, Burch J L
Swedish Institute of Space Physics, Uppsala 75121, Sweden.
Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Phys Rev Lett. 2021 Nov 19;127(21):215101. doi: 10.1103/PhysRevLett.127.215101.
We report in situ observations of an electron diffusion region (EDR) and adjacent separatrix region in the Earth's magnetotail. We observe significant magnetic field oscillations near the lower hybrid frequency which propagate perpendicularly to the reconnection plane. We also find that the strong electron-scale gradients close to the EDR exhibit significant oscillations at a similar frequency. Such oscillations are not expected for a crossing of a steady 2D EDR, and can be explained by a complex motion of the reconnection plane induced by current sheet kinking propagating in the out-of-reconnection-plane direction. Thus, all three spatial dimensions have to be taken into account to explain the observed perturbed EDR crossing. These results shed light on the interplay between magnetic reconnection and current sheet drift instabilities in electron-scale current sheets and highlight the need for adopting a 3D description of the EDR, going beyond the two-dimensional and steady-state conception of reconnection.
我们报告了对地球磁尾中一个电子扩散区（EDR）及相邻分界线区域的原位观测结果。我们观测到在较低混合频率附近有显著的磁场振荡，其传播方向垂直于重联平面。我们还发现，靠近EDR的强烈电子尺度梯度在相似频率下呈现出显著振荡。对于稳定二维EDR的穿越，这种振荡是无法预期的，并且可以通过电流片扭结在重联平面外方向传播所引发的重联平面复杂运动来解释。因此，必须考虑所有三个空间维度才能解释观测到的受扰EDR穿越。这些结果揭示了电子尺度电流片中磁重联与电流片漂移不稳定性之间的相互作用，并突出了超越重联的二维和稳态概念，采用EDR的三维描述的必要性。
