Long-term changes in the nightly behaviour of the oxygen red 630.0 nm line nightglow intensity and trends in the thermospheric meridional wind velocity

Abstract

Long-term changes in the nightly behaviour of the monthly/seasonal mean of the oxygen red 630.0 nm line intensity were observed at Abastumani (41.75° N, 42.82° E) from 1957 to 1993. The long-term increase in the red-line intensity after twilight and decrease at midnight is also mostly accompanied by an increase in the intensity before morning twilight. Using changes in mean seasonal nightly behaviour of the red-line intensity combined with the observed night-time negative trend in the ionosphere F2 layer peak height (hmF2) at Tbilisi (41.65° N, 44.75° E) from 1963 to 1986, the trend in the meridional component of thermospheric wind velocity is estimated. The obtained positive trend in the northward wind velocity (or decrease in the southward wind velocity) has a higher value in winter, where the hmF2 height decrease and the midnight/after midnight decrease in the red-line intensity are larger, and has lower values in spring and summer, where the decrease in hmF2 and midnight red-line intensity are comparatively smaller.

Acknowledgements

This work has been supported by GNSF/ST07/5-208 and GNSF/PRES08/5-330.