Response of the mesopause airglow to solar activity inferred from measurements at Zvenigorod, Russia

Ground-based spectrographical observations of infrared emissions of the mesopause region have been made at Zvenigorod Observatory (56 N, 37 E), located near Moscow, Russia, for 670 nights of 2000–2006. The characteristics of the hydroxyl and molecular oxygen (865 nm) airglow, heights of which correspond to 87 and 94 km, are analyzed for finding their response to solar activity. The measured data exhibit a response to the F10.7 solar radio flux change, which is 30%–40%/100 sfu in intensities of the emissions and about 4.5 K/100 sfu in hydroxyl temperature. Seasonal variations of the airglow response to solar activity are observed. In winter it is more significant than in summer. Mechanisms that may provide an explanation of the solar influence on intensities of the emissions and temperature are considered. Radiative processes not involving atmospheric dynamics appear insufficient to explain the observed effect.