The Mg II equatorial airglow altitude distribution

Four occasional measurements of the altitude distribution of the 2796–2803‐Å doublet equatorial airglow have been made with the astronomical TD‐1A satellite during winter 1973–1974. The observations indicate the presence of layers of Mg + ions in the evening twilight F region in the African sector. Horizontal column densities reaching 8 × 10 9 Mg + ions/cm² are observed with peak altitudes varying from 230 to 480 km. Steep topside gradients with scale heights of about 5 km are observed on three occasions.