Investigation of sodium in the upper atmosphere

Abstract

Upper atmospheric atomic sodium abundances have been measured near Ankara (39.9°N, 32.6°E), Turkey, from February 1976 to April 1977. The daytime absorption measurements were made with a Pepsios spectrometer using the solar radiation near the D2 line of sodium at 5890 Å. Seasonal and daily variations of the sodium abundance were examined. A seasonal variation appears to be present with maximum abundance values occurring near the end of February and minimum values occurring in April. No significant evidence was found for diurnal variations. However, there is some evidence for shorter‐period fluctuations with periods between 25 and 108 min. A model is proposed in which the atomic sodium has a cloudlike structure, and the parameters obtained in this way suggest that the ‘clouds’ have a mean column density of 1.5×109 atoms/cm2.