No abstract

No abstract

No abstract

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 × 109 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.

The interstellar extinction law in the far ultraviolet has been derived from observations of about 100 stars for three galactic regions in the direction of Cygnus, galactic centre and anticentre. For each region the weighted mean extinction curve has an accuracy of about 6 % and shows no variation for the different directions. The profile of the broad extinction band centred near 2200 A is derived and shown to be symmetrical. It is concluded that the extinction characteristics will need more than one type of particle for their explanation.