Influence of the ionosphere F2 layer peak height hmF2 long-term lowering on the mean night variation in the red 630.0 nm line nightglow intensity

Didebulidze, G., Gudadze, N., Lomidze, L. and Javakhishvili, G.

Georgian National Astrophysical Observatory (former Abastumani Astrophysical Observatory), Tbilisi, Georgia

The long-term variations in the ionosphere F2 layer peak height (hmF2) for day- and night-time conditions and for different seasons is investigated using Tbilisi (41.65 N, 44.75 E) ionosonde data obtained in 1963-1986. The revealed lowering of hmF2 is compared with the oxygen red 630.0 nm line total nightglow intensity seasonal and night long-term variations at Abastumani (41.75 N; 42.82 E) in 1957-1993. The long-term increase in the 630.0 nm intensity observed after astronomical twilight for most seasons and its decrease during midnight is considered as a result of the lowering of the ionosphere hmF2 peak height. The different values of the red line intensity long-term change (increasing trend after twilight and decreasing at midnight) in different seasons may result from the meridional wind velocity long-term changes. By using a simple Chapman type (damping in time) layer for the ionosphere F2 region electron density height distribution, which takes into account a meridional wind velocity, an estimation of the lowering of the ionosphere peak height for any month and corresponding red line intensity nighttime behaviour is done.