磁岛合并的演化

he merging of magnetic islands plays an important role in magnetic reconnection. In this paper, two-dimensional (2D) particle-in-cell (PIC) simulations are performed to investigate the coalescence process of magnetic islands in collisionless plasma. We find that the merging of magnetic islands have two stages: In the first stage, the two islands approach each other slowly due to the attractive force between the homodromous currents. The electrons around the merging line are accelerated by the out-of-plane electric field, and then a thin current sheet is formed, where the magnetic field is also piled up. In the second stage, the fast magnetic reconnection occurs in the thin current sheet around the merging line, and the resulted electromagnetic structures around the merging line are similar to those in reconnection diffusion region formed in a Harris current sheet, where the most characteristic is the quadrupole structure of the out-of-plane magnetic field.