Observation of a Knotted Electron Diffusion Region in Earth's Magnetotail Reconnection
Abstract
Magnetic reconnection is a fundamental plasma process that alters the magnetic field topology and releases magnetic energy. Most numerical simulations and spacecraft observations assume a two-dimensional diffusion region, with the electron diffusion region (EDR) embedded in the same plane as the ion diffusion region (IDR) and a uniform guide field throughout. Using observations from Magnetospheric Multiscale (MMS) mission, we report a non-coplanar, knotted EDR in Earth's magnetotail current sheet. The reconnection plane of the knotted EDR deviates by approximately 38{\deg} from that of the IDR, with the guide field exhibiting both a 38{\deg} directional shift and a twofold increase in amplitude. Moreover, the Hall magnetic field is bipolar in the EDR but quadrupolar in the IDR, indicating different Hall current structures at electron and ion scales. These observations highlight the importance of three-dimensional effects and illustrate the complexity of multiscale coupling between the EDR and IDR during reconnection studies.1
Keywords
Cite
@article{arxiv.2507.10842,
title = {Observation of a Knotted Electron Diffusion Region in Earth's Magnetotail Reconnection},
author = {Xinmin Li and Chuanfei Dong and Hantao Ji and Chi Zhang and Liang Wang and Barbara Giles and Hongyang Zhou and Rui Chen and Yi Qi},
journal= {arXiv preprint arXiv:2507.10842},
year = {2026}
}
Comments
27 pages and 4 figures