Seasonal and Long-Term Changes in the Intensity of O2(b1Σ) and OH(X2Π) Airglow in the Mesopause Region

Spectral observations of the mesopause airglow at the Zvenigorod Scientific Station have been used to obtain the midnight emission intensities of molecular oxygen (О 2 А(0-1) band) and hydroxyl (OH (6-2) band) for 2000–2019. Spectral analysis of the variations has made it possible to determine the annual variability for each emission, which is described by the sum of four harmonics. The time lag in seasonal variations of the hydroxyl emission relative to variations in the emission of molecular oxygen is 5–18 days. Long-term changes in the average annual emission intensities have been studied. The linear trend (–3.3 ± 0.3% per year for О 2 А(0-1) and –2.6 ± 0.2% per year for ОН(6-2)), the dependences on the 11-year solar cycle (response to changes in the Lyman-alpha solar radiation (18.5 ± 3.3% per 10 11 photons cm –2 s –1 for О 2 А(0-1) and 10.5 ± 2.5% per 10 11 photons cm –2 s –1 for OH (6-2)) and the 22-year solar cycle (response to changes in the solar magnetic field strength (23.2 ± 4.5% per 100 μТ for О 2 А(0-1) and 12.1 ± 3.5% per 100 μТ for ОН (6-2)), as well as quasi-eight-year oscillations have been found.