A comparison of fluid and kinetic models of steady magnetic reconnection

For steady magnetic reconnection in a current sheet, a two-fluid model that includes tensor pressure is compared with kinetic simulations. The kinetic simulations model a Harris sheet in two dimensions with prescribed inflow and free outflow. The two-fluid model provides solutions along the symmetry line from the inflow boundary to the flow stagnation point. The model assumes incompressibility and neglects the Hall current. Profiles from the inflow boundary to the X-point of the out-of-plane electric field and the terms in Ohm’s law that contribute to it from the simulation and from the fluid model agree in almost every detail. The best agreement is obtained when relaxation of the tensor pressure to isotropy occurs on time scales comparable to the electron plasma period. On ion scales, the two-fluid and kinetic simulations give similar results when finite Larmor radius physics is included. The ion pressure relaxation scales linearly with the ion/electron mass ratio.