We present a large-scale model of the parallel electric fields in the upward current region of the aurora. The model, called the Transition Layer Model, applies to intense, discrete arcs. It is based on 1-D spatial, 2-D velocity static Vlasov simulations and observations from the Fast Auroral Snapshot (FAST) satellite. The model depicts three regions along the magnetic field that are separated by two transition layers which contain parallel electric fields. The current-voltage properties closely follow the Knight relation. ¿ 2000 American Geophysical Union