Journal Article

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

Xiong, Q. Y., Xu, S. B., Jiang, K., Wei, Y. Y., Huang, S. Y., Zhang, J., Yuan, Z. G.

2024

Overview

Using high‐resolution data from the Magnetospheric Multiscale mission, an electron‐only reconnection current sheet is found between two successive dipolarization fronts (DFs). The electron‐only reconnection occurs between the northward component of the magnetic field of the flux pileup region (FPR) of the first DF (DF1) and the southward component of the magnetic dip of the second DF (DF2). The faster DF2 compresses the FPR of DF1, which constitutes an anti‐parallel topology and reduces the thickness of the current sheet. Further analysis shows that the current sheet is unstable to the electron tearing instability, which may power the onset of the reconnection. Our results suggest that these two DFs may merge into one by the reconnection, which sheds light on the evolution of DFs during their earthward propagation. Plain Language Summary Magnetic reconnection, releasing magnetic energy and energizing plasmas, are believed to be responsible for the explosive phenomena in space. Though reconnection has been investigated for decades, the onset of reconnection is elusive. Dipolarization fronts (DFs), important carriers in the transportation of mass, magnetic flux, and energy in the magnetotail, can be generated by reconnections and will integrate into the geomagnetic field at last. The generation of DFs and dynamics at DFs are thoroughly probed by simulations and observations. However, the evolution of DFs during their earthward propagation is rarely inspected. In this work, we present an observation of an electron‐only reconnection between two successive DFs. The latter DF compresses the former DF and reduces the thickness of the current sheet between them. Inside the reconnection current sheet, electron tearing instability is unstable, which may power the reconnection. By reconnection, these two DFs may merge. Our observations can improve our understanding of the evolution of DFs in the magnetotail. Key Points An electron‐only reconnection current sheet is found between two dipolarization fronts The current sheet is unstable to the electron tearing instability DF2 compresses DF1 and thins the current sheet, which may initiate electron tearing instability and trigger the reconnection

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Current sheets / Eigenvalues / Electrons / Evolution / Fronts / Geomagnetic field / Magnetic field / Magnetic fields / Magnetic flux / Magnetic inclination / Magnetic reconnection / Magnetospheres / Magnetotails / Plasma / Tearing / Thickness / Topology