The day-sector polar F-layer during a magnetospheric substorm

Ionogram and all-sky camera data have been recorded on the Air Force Cambridge Research Laboratories' Flying Ionospheric Laboratory in the day sector of the auroral oval under conditions of darkness. The airborne measurements show that the polar F-layer irregularity zone, which is characterized on ionograms by a generally non-retarded and spread F type echo, exhibits meridional motions similar to the day-sector auroras. The polar F-layer irregularity zone and the day-sector auroras move equatorward and then move poleward in harmony with the development and decay of a magnetospheric substorm. We suggest that the polar cusp also moves in essentially the same fashion.