Correlation between the 5577 Å [OI] night airglow intensity and solar activity

Abstract

Several prior studies have demonstrated correlations between both mean annual and mean monthly intensities of the 5577 Å [OI] line of the night airglow and corresponding means of solar activity, expressed in terms of sunspot area or sunspot number. We have analysed green line intensity measurements obtained at Sacramento Peak, New Mexico (32°43'N; 105°45'W) from November 1956 to June 1963 for correlation with two indices of solar activity, Zurich relative sunspot numbers and 10.7-cm solar flux. The analysis was performed on both a mean monthly and mean nightly basis and was further subdivided (arbitrarily) in terms of solar cycle phase. We have found that: (1) a statistically significant positive correlation exists between monthly and nightly averages of green line activity and both indices of solar activity; (2) the 10.7-cm flux shows a somewhat higher correlation with green line activity than is shown by Zurich relative sunspot number; (3) the degree of correlation is dependent on the phase of the solar cycle. It is suggested that other studies of solar activity and geophysical parameters might also show similar variations as a function of solar cycle phase.