Observations of Energy Conversion Caused by Magnetic Reconnection at a Dipolarization Front

Abstract

Dipolarization fronts (DFs) are widely believed to host energy conversion processes. However, which mechanism is responsible for the energy conversion is still obscure. Using data from the Magnetospheric Multiscale mission, a current sheet is observed at a DF. This current sheet is caused by interchange instability bending the edge of the DF. Inside the current sheet, Hall electromagnetic field, super Alfvénic electron jets, demagnetization of ions and electrons, strong energy conversion, and steady ion flow and temperature are observed, indicating an electron‐only reconnection at the DF. The duskward plasma flow, which may be deflected by the DF, compresses the bent edges of the DF. As a result, the width of the current sheet between two adjacent bent edges of the DF reduces, and then reconnection begins. Our observations give direct evidence that magnetic reconnection results in energy conversion at a DF.

In Situ Observations of Magnetic Reconnection Caused by the Interactions of Two Dipolarization Fronts

“…The typical features of a DF include an abrupt increase of B z within a short duration, a decrease in plasma density, and earthward plasma flow (e.g., Runov et al, 2009). Abundant dynamic processes are found at and around DFs, such as sub-structures at DFs (Fu et al, 2012;Jiang et al, 2020;Sun et al, 2014), plasma waves and instabilities (Huang et al, 2012;Huang et al, 2019;Pritchett & Coroniti, 2010;Yu et al, 2022;Zhou et al, 2009;Zhou, Ni, et al, 2014), energy conversion (Angelopoulos et al, 2013;Jiang et al, 2024;Zhong et al, 2019), and electron acceleration (Fu et al, 2011;Wei et al, 2023;Y. Xu et al, 2018;.…”