# Quasi-separatrix Layers Induced by Ballooning Instability in Near-Earth Magnetotail

## TL;DR

This study investigates how 3D ballooning instability in the near-Earth magnetotail induces reconnection through the formation of quasi-separatrix layers, revealing the intrinsic 3D nature of these processes and offering a new way to identify reconnection sites.

## Contribution

It applies a solar physics algorithm to analyze 3D QSLs in the magnetotail, demonstrating their correlation with plasmoid formation and reconnection during ballooning instability.

## Key findings

- QSL distribution closely follows plasmoid formation.
- Strong coupling between ballooning and reconnection processes.
- 3D QSL geometry can identify reconnection sites.

## Abstract

Magnetic reconnection processes in the near-Earth magnetotail can be highly 3-dimensional (3D) in geometry and dynamics, even though the magnetotail configuration itself is nearly two dimensional due to the symmetry in the dusk-dawn direction. Such reconnection processes can be induced by the 3D dynamics of nonlinear ballooning instability. In this work, we explore the global 3D geometry of the reconnection process induced by ballooning instability in the near-Earth magnetotail by examining the distribution of quasi-separatrix layers associated with plasmoid formation in the entire 3D domain of magnetotail configuration, using an algorithm previously developed in context of solar physics. The 3D distribution of quasi-separatrix layers (QSLs) as well as their evolution directly follows the plasmoid formation during the nonlinear development of ballooning instability in both time and space. Such a close correlation demonstrates a strong coupling between the ballooning and the corresponding reconnection processes. It further confirms the intrinsic 3D nature of the ballooning-induced plasmoid formation and reconnection processes, in both geometry and dynamics. In addition, the reconstruction of the 3D QSL geometry may provide an alternative means for identifying the location and timing of 3D reconnection sites in magnetotail from both numerical simulations and satellite observations.