Ionospheric Magnetic Field Measurements at Auroral Latitudes

The magnetometer data from five sounding rocket flights launched from Fort Churchill under a variety of auroral conditions are discussed. The data have been interpreted in terms of model currents which would reproduce the observed magnetic field variations.It was found in some cases that the current systems inferred from the rocket magnetometer were too weak to account for the ground-based magnetometer observations. This suggests that ionospheric current systems must occupy a much larger spatial extent than has generally been assumed in the past.