  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.
