Long-term behavior of magnesium ions in the upper atmosphere has been observed at wavelengths near 2800 Angstrom using the Nimbus 7 solar backscattered ultraviolet (SBUV) instrument. Observations were made in the continuous spectral scan mode that operated approximately once a month from 1979 to 1986. Total column abundance of Mg+ near local noon is the quantity derived from the nadir-viewing SBUV observations, Mg+ total column abundances vary as a function of magnetic activity, solar sunspot activity, season, dip latitude, and longitude, as the result of changes in chemistry and ion transport. Increased Mg+ column abundances are observed during periods of high magnetic activity at all latitudes. Total Mg+ column abundances are observed to increase with solar sunspot activity at low and middle latitudes. Seasonal variation in the midlatitude Mg+ column abundance is observed with a maximum near summer solstice. The total column abundances derived here are complementary to previous metallic ion studies in the upper E and F regions.
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