Observations of an Electron Diffusion Region in Symmetric Reconnection with Weak Guide Field
Observations of an Electron Diffusion Region in Symmetric Reconnection with Weak Guide Field
复制标题
DOI：
10.3847/1538-4357/aaf16f
复制
发表时间：
2019-01
期刊：
影响因子：
--
通讯作者：
M. Zhou;X. Deng;Z. Zhong;Y. Pang;R. X. Tang;M. El‐Alaoui;R. Walker;C. Russell;G. Lapenta-G.-La
中科院分区：
文献类型：
--
作者：
M. Zhou;X. Deng;Z. Zhong;Y. Pang;R. X. Tang;M. El‐Alaoui;R. Walker;C. Russell;G. Lapenta-G.-La
磁层多尺度航天器在地球磁尾的对称重联中遇到了电子扩散区（EDR）。 EDR包含约2nT的引导场，是流入区域磁场的13%，其厚度约为2个局域电子惯性长度。观察到与该 EDR 相关的强烈能量耗散、超阿尔芬尼电子射流、电子非回旋性和新月形电子速度分布。这些特征与白天磁层顶不对称重联中 EDR 的特征相似。电子从 EDR 的直接上游获得了大约 50% 的能量。在 EDR 的边界处可以看到新月形电子分布，而 EDR 内部高度弯曲的磁场线可能使电子旋转。 EDR 的特点是由反平行漂移电子携带的平行电流，这些电子可能被沿引导场的平行电场加速。这些结果揭示了 EDR 的基本电子物理，并提供了 EDR 与弱导场对称重联的重要示例。
The Magnetospheric Multiscale spacecraft encountered an electron diffusion region (EDR) in a symmetric reconnection in the Earth’s magnetotail. The EDR contained a guide field of about 2 nT, which was 13% of the magnetic field in the inflow region, and its thickness was about 2 local electron inertial lengths. Intense energy dissipation, a super-Alfvénic electron jet, electron nongyrotropy, and crescent-shaped electron velocity distributions were observed in association with this EDR. These features are similar to those of the EDRs in asymmetric reconnection at the dayside magnetopause. Electrons gained about 50% of their energy from the immediate upstream to the EDR. Crescent electron distributions were seen at the boundary of the EDR, while highly curved magnetic field lines inside the EDR may have gyrotropized the electrons. The EDR was characterized by a parallel current that was carried by antiparallel drifting electrons that were probably accelerated by a parallel electric field along the guide field. These results reveal the essential electron physics of the EDR and provide a significant example of an EDR in symmetric reconnection with a weak guide field.