Twilight observations of upper atmospheric sodium, potassium, and lithium

Abstract

Twilight resonance emissions due to atmospheric sodium, lithium, and potassium have been measured for over one year. The existence of the potassium resonance line was verified by using an absorption cell.Several problems of measuring the emissions and of subsequently calculating a density distribution are discussed. The widths of about 13 km and the topside scale heights of about 4.5 km obtained for the sodium layer are significantly less than obtained at Saskatoon in previous measurements. Atmospheric transmission functions have been recalculated with the results that the sodium and lithium layers are both at about the same height of around 90 km. A lower height of about 85 km was obtained for the potassium layer.The seasonal variations of sodium and lithium twilight abundances are shown to be similar with additional sharp enhancements of lithium abundances thought to be due to natural and man-made injections of lithium. Any seasonal variations of the potassium abundances in the lower layer were masked by large day-to-day fluctuations.