Characteristics of Magnetic Reconnection With a Finite X-Line Length

The characteristics of magnetic reconnection with a finite x-line length are studied using three-dimensional (3D) particle-in-cell (PIC) simulations. We simulate two cases: anti-parallel reconnection and guide field reconnection. In both cases, reconnection is triggered by an initial perturbation that is localized in the current direction, and then, an active reconnection region extending around 20 ion inertia length along the current direction is developed. In both cases, the electron inertia term plays an important role in balancing the reconnection electric field near the two edges of the x-line along the current direction. On the ion drifting side, ions are heated while electron heating is not significant; while on the electron drifting side, electrons are heated while ion heating is weak. In the anti-parallel case, the out-of-plane Hall magnetic field on the ion and electron drifting side of the reconnection region shows reversed polarization, while in the guide field case, the in-plane Hall electric field shows reversed polarization. These features can be used as identifications for reconnection with a finite x-line length during observations in the magnetotail, they also provide an estimation of the satellite location in the dawn-dusk direction of the reconnection region.