Driven reconnection about a magnetic X point in weakly collisional plasmas

The effect of the Hall term in the process of forced magnetic reconnection for an X point magnetic field configuration, both in the collisionless limit and in the case of weak resistive dissipation, is investigated in this paper. In the case of no guide field, a two-fluid (four fields) linearized model is derived and solved as a forced initial-value problem, resulting in an unexpected insensitivity of the reconnective rates (either asymptotic or peaked) upon the ion skin depth di which characterizes the Hall term. This result is obtained by imposing the axial current density and magnetic field perturbations to vanish at the boundary of the system. In the collisionless limit, the influence of the Hall term resides in the spatial configuration of the fields, which presents an interesting phase-mixing dynamics with three nested layers of width of the order of de2/di, de, and di, with de being the electron skin depth. The first scale length arises due to the coupling between axial and perpendicular motion and is characterized by high frequency oscillations superimposed on a low-frequency carrier. In the weakly collisional limit, resistivity smooths out the high frequency oscillations typical of the innermost layer