Three-dimensional evolution of the fast reconnection mechanism in a sheared current sheet

Abstract

Extending the previous simulation model with the plane symmetry boundaries, the present paper studies the three-dimensional (3D) fast reconnection evolution in the presence of an initial sheared field by employing the axis symmetry boundary conditions. The fast reconnection evolution for the open system, where the reconnection outflow is open to free space, is not significantly influenced by the sheared field, although for the larger magnitude of the sheared field its onset time is more delayed and the fast reconnection process tends to proceed more steadily. In any case, the diffusion region remains to be localized around the X neutral line, and the fast reconnection outflow jet is accelerated to the Alfven velocity by standing slow shocks. The initial sheared field lines are swept away by the reconnection jet, and attached to the jet, a large-scale plasmoid is formed and propagates outward. In the plasmoid, the reconnected sheared field lines are accumulated near the interface between the reconnection jet and the plasmoid, and the sheared field is piled up in the form of a core. The 3D plasmoid propagation is considerably distorted in the direction of the sheared magnetic field since the plasma tends to be accelerated along the sheared field lines.