Effect of solar ultraviolet radiation on excitation of 630 nm nightglow emissions

It is common knowledge that the 630 nm emission intensity in the night airglow at middle latitudes increases more than twice during solar maximum. This phenomenon was assumed to be caused by variations in intensity of solar ultraviolet radiation during different solar cycles [Fishkova, 1983]. This paper presents results of photometric measurements of the night-sky emission intensity at the latitude of 63°, meridian of Yakutsk (130° E), in 1990-2007. We show dependence of the 630 nm emission intensity under quiet geomagnetic conditions on solar activity during the 22nd and 23rd solar cycles. A close connection between intensity of the nightglow 630 nm line and intensity of the extreme ultraviolet (EUV) solar radiation was established from SOHO/SEM data (1997-2007) with the correlation coefficient 0.8-0.9. Thus, we obtained experimental evidence for the dominant role of the solar EUV in provoking 630 nm nightglow emissions.