Extension of Electron Dissipation Region along the Downstream Direction in Steady Collisionless Driven Reconnection

Steady collisionless driven reconnection in an open system is investigated by means of 3D fullparticle simulations. When the system relaxes to the steady state, a long and narrow current sheet and electron dissipation region are formed in the downstream direction. The Sweet-Parker model predicts that outflow peak will appear at the edge of electron dissipation region. However, the electron dissipation region still extends far away from the peak position toward the downstream direction, which is due to the strong electron outflow. The reason why such a two-scale structure is maintained in the steady state is investigated from a viewpoint of energy conversion. It is found that the dissipated magnetic energy is converted firstly to electron kinetic energy in the driving electric field direction at the reconnection point, and then most of this energy is converted to electron outflow kinetic energy during electrons move towards the edge of the inner structure of the electron dissipation region in the downstream direction.