Multiple X line reconnection: 2. The dynamics

The plasma dynamics associated with both the single and multiple X line reconnection processes is studied based on an MHD simulation. It is found that the plasma dynamics in the single X line reconnection is generally consistent with the reconnection models by Petschek and Sonnerup. However, the outflow plasma speed is considerably smaller than the upstream Alfvén speed predicted by the theoretical models. In the case of multiple X line reconnection, repeated formation and convection of magnetic islands are observed with a recurrence time τ ≃ 10tA/Ro, where tA is the Alfvén transit time, and Ro = V1/VA is the imposed driving rate. The magnetic reconnection process is found to be impulsive and intermittent. An exponential growth of the reconnection rate is observed during the impulsive phase. The simulation results are generally consistent with satellite observations of flux transfer events (FTE's). The BN signature associated with the FTE's is observed in our simulation. Magnetic flux tubes with a cross section of ∼1 RE² are found to occur repeatedly every 5–15 min in our simulation.