Collisionless driven reconnection in an open system

Particle simulation studies of collisionless driven reconnection in an open system are presented. Collisionless reconnection evolves in two steps in a ccordance with the formation of two current layers, i.e., an ion current la yer in the early ion phase and an electron current layer in the late electr on phase. After the electron current layer is formed inside the ion current layer, the system relaxes gradually to a steady state when convergent plas ma flow is driven by an external electric field with a narrow input window. On the other hand, when the convergent plasma flow is driven from the wide input window, magnetic reconnection takes place in an intermittent manner, due to the frequent formation of magnetic islands in the vicinity of neutr al sheet.