Near-Earth magnetic disturbance in total field at high latitudes 1. Summary of data from Ogo 2, 4, and 6

Variations in the total (i.e., scalar) magnetic field data from the polar orbiting Ogo 2, 4, and 6 spacecraft (altitudes 400–1510 km) are summarized for invariant latitudes above 55° Data from all degrees of magnetic disturbance are included. The data are presented in terms of the quantity ΔB (i.e., measured field magnitude minus the field magnitude from a spherical harmonic model of the quiet field). The total field variations at the satellite form two regions: a region of positive ΔB between about 2200 and 1000 MLT with its maximum near 0300 and 72° and a region of negative ΔB between about 1000 and 2200 MLT with its maximum near 1500 and 75°. In the negative ΔB region, |ΔB| is greatest in summer and least in winter and shows a substantial decrease with increasing altitude. The |ΔB| in the positive ΔB region, on the other hand, shows no seasonal variation and only a small decrease with increasing altitude. The |ΔB| increases with the Ap index in both regions.