Electron Diffusion Regions in Magnetotail Reconnection Under Varying Guide Fields

[摘要] Kinetic structures of electron diffusion regions (EDRs) under finite guide fields in magnetotail reconnection are reported. The EDRs with guide fields 0.14–0.5 (in unit of the reconnecting component) are detected by the Magnetospheric Multiscale spacecraft. The key new features include the following: (1) cold inflowing electrons accelerated along the guide field and demagnetized at the magnetic field minimum while remaining a coherent population with a low perpendicular temperature, (2) wave fluctuations generating strong perpendicular electron flows followed by alternating parallel flows inside the reconnecting current sheet under an intermediate guide field, and (3) gyrophase bunched electrons with high parallel speeds leaving the X‐line region. The normalized reconnection rates for the three EDRs range from 0.05 to 0.3. The measurements reveal that finite guide fields introduce new mechanisms to break the electron frozen‐in condition.

[发布日期] 2019-06-07

[学科分类] 地质物理学

[关键词] ELECTRON DIFFUSION;KINETICS;MAGNETIC FIELD RECONNECTION;EARTH MAGNETOSPHERE;MAGNETOSPHERIC MULTISCALE (MMS) MISSION;GEOMAGNETIC TAIL;MAGNETOTAILS;MAGNETIC FLUX