Solar flux and seasonal variations of the mesopause temperatures at 51°N

Observations of the OH (8-3) band airglow emission, using a multichannel tilting filter type photometer, have been carried out at Calgary (51°N, 114°W), Canada, since 1981. In this paper recent measurements of the nocturnal, seasonal and solar flux variations of the mesopause temperature, obtained from the rotational temperature of the OH (8-3) band observations, are presented. The data presented span the ascending phase of the present solar cycle viz. 1987–1988 (low solar activity) and 1990 (high solar activity). Good correlations (r = 0.73) between the OH (8-3) band rotational temperature and the 10.7 cm solar flux were observed. The mean temperature for the period investigated was about 210 K. The seasonally averaged nocturnal variations show only small irregular excursions, possibly associated with solar tides and the passage of gravity waves in the mesopause region. However, the observed rotational temperatures show considerable night-to-night changes.