The average equatorward component of the perpendicular electric field between the dusk plasmapause and polar cap has been determined at seven altitudes below 8000 kilometers by averaging large scale electric field measurements made on 166 passes of the S3-3 satellite through the dusk auroral zone. The observed variation of the perpendicular electric field with altitude and latitude requires the presence of an upward pointing parallel electric field over a latitude range of a few degrees centered near 70 ¿ invariant latitude, and with a maximum parallel potential of several kilovolts.