Ultraviolet observations of equatorial dayglow above the F[SUB]2[/SUB] peak.

Ultraviolet emissions above 540 km have been detected in the equatorial zone at a local
time near 1800 with instruments aboard the TD1 A astronomical satellite. The main features
of the emissions can be accounted for by resonance scattering of sunlight by Mg + ions.
The observations confirm previous mass spectrometric measurements of metallic ions in the
equatorial ionosphere and generally are consistent with the vertical transport mechanism
proposed by Hanson and others. The emissions often are highly asymmetrical with respect
to the magnetic dip equator, possibly indicating the effect of transequatorial neutral winds.
Additional weaker equatorial emissions have been tentatively identified with Fe +, O +, and
possibly Si + ions geographically distinct from the Mg + ions.