We have simulated externally drived reconnection by solving the magnetohydrodynamic equations in a three-dimensional, tail-like geometry. As reconnection proceeds, the tail current is interrupted locally and field aligned currents are generated. The field aligned current flows towards the ionosphere on the morning side and away from the ionosphere in the evening. The field aligned currents flow in a narrow band at the outer edge of the plasma sheet. Thus, the simulation demonstrates that the nightside substorm current system is a natural consequence of the driven reconnection model.