Abstract
Abstract. Long-term observations of total nightglow intensity of the atomic oxygen red 630.0 nm line at Abastumani (41.75° N, 42.82° E) in 1957–1993 and measurements of the ionosphere F2 layer parameters from the Tbilisi ionosphere station (41.65° N, 44.75° E) in 1963–1986 have been analyzed. It is shown that a decrease in the long-term trend of the mean annual red 630.0 nm line intensity from the pre-midnight value (+0.770±1.045 R/year) to its minimum negative value (−1.080±0.670 R/year) at the midnight/after midnight is a possible result of the observed lowering of the peak height of the ionosphere F2 layer electron density hmF2 (−0.455±0.343 km/year). A theoretical simulation is carried out using a simple Chapman-type layer (damping in time) for the height distribution of the F2 layer electron density. The estimated values of the lowering in the hmF2, the increase in the red line intensity at pre-midnight and its decrease at midnight/after midnight are close to their observational ones, when a negative trend in the total neutral density of the upper atmosphere and an increase in the mean northward wind (or its possible consequence – a decrease in the southward one) are assumed.
Highlights
Search for long-term trends of the atmosphere/ionosphere parameters is of vital importance for study of many solarterrestrial coupling processes
The long-term increase in thermospheric mean northward wind velocity can provoke the downward motion of the ionosphere F2 layer and cause of different long-term trends in the red line intensity emitted from this region (Table 1). We investigate this phenomenon by use of the analytic expression for the height distribution of the mid-latitude nighttime ionosphere F2 layer electron density Ne(h, t) (Didebulidze and Pataraya, 1999): zα z
The above consideration shows that the positive trend in the oxygen red 630.0 nm line intensity at pre-midnight and its negative value at midnight/after midnight, observed at Abastumani could be caused by negative trend in the peak height hmF2 of the ionosphere F2 layer, which was observed from the Tbilisi ionosphere station
Summary
Search for long-term trends of the atmosphere/ionosphere parameters is of vital importance for study of many solarterrestrial coupling processes. The presence of the negative long-term trend of the ionosphere F2 layer electron density peak height hmF2 was detected at many ionosphere stations in different regions of the world (Ulich and Turunen, 1997; Bremer, 1998; Jarvis et al, 1998; Marin et al, 2001; Xu et al, 2004) This lowering of the ionosphere F2 layer may be the result of global cooling of the upper atmosphere (Roble and Dickinson, 1989; Rishbeth, 1990) and related changes in its dynamics. A theoretical estimation of influence of the mean northward wind increase or decrease in the southward on lowering the hmF2 and accompanying difference between the premidnight and midnight/after midnight long-term trends of the oxygen red 630.0 nm line intensity will be made
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
