Abstract
Abstract. A digital CCD all-sky spectrograph was made by the Polar Geophysical Institute (PGI) to support IPY activity in auroral research. The device was tested at the Barentsburg observatory of PGI during the winter season of 2005–2006. The spectrograph is based on a cooled CCD and a transmission grating. The main features of this spectrograph are: a wide field of view (~180°), a wide spectral range (380–740 nm), a spectral resolution of 0.6 nm, a background level of about 100 R at 1-min exposure time. Several thousand spectra of nightglow and aurora were recorded during the observation season. It was possible to register both the strong auroral emissions, as well as weak ones. Spectra of aurora, including nitrogen and oxygen molecular and atomic emissions, as well as OH emissions of the nightglow are shown. A comparison has been conducted of auroral spectra obtained by the film all-sky spectral camera C-180-S at Spitsbergen during IGY, with spectra obtained at Barentsburg during the last winter season. The relationship between the red (630.0 nm) and green (557.7 nm) auroral emissions shows that the green emission is dominant near the minimum of the solar cycle activity (2005–2006). The opposite situation is observed during 1958–1959, with a maximum solar cycle activity.
Highlights
The spectral characteristics of auroral luminosity inside polar caps differ from that measured in the main auroral ovals
It is shown that the character of the auroral luminosity in the minimum of solar activity changes significantly compared to the period of high solar activity
The red type A aurora occurrence rate is negligible relative to the occurrence rate of the green aurora near the minimum of solar activity cycle while those occurrence rates are nearly equal near the maximum of solar activity (Fig. 6)
Summary
The spectral characteristics of auroral luminosity inside polar caps differ from that measured in the main auroral ovals. The main difference is that in the polar caps the intensity of integral luminosity and of some auroras is significantly lower than in the auroral oval. A large region of red luminosity in the emissions 630.0–636.4 nm (Yevlashin, 1961; Sandford, 1961; Sandholt et al, 1993, 2002) appears near the northern boundary of the oval. The aim of this paper is to present a new CCD all-sky spectral camera S-180. A preliminary estimation of the characteristics of auroral luminosity in the emissions 557.7 nm and 630.0 nm are presented. The data are observed in the polar cap of the Northern Hemisphere at Barentsburg ( ∼74.4◦ N, ∼130.7◦ E) during the minimum of solar activity (2005–2006) using the new spectrograph. A comparison of these spectra with the ones which had been registered in the years of very high solar activity (1958–1959) in Pyramida ( ∼74.7◦ N, ∼130.8◦ E) is presented
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