Naslov
Measurements of the He I 1083 nm Line on the Sun During Different Solar Activity Phases: in the Years 1993 and 1995

Autori
Jurdana-Šepić, Rajka ; Brajša, Roman ; Šaina, B. ; Woehl, H.

Izvornik
Central European Astrophysical Bulletin (1845-8319) 33 (2009), 1; 337-358

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Sun - He I 1083 nm line

Sažetak
Latitudinal variations and North--South asymmetry of the He~I 1083 nm line across the solar disc are investigated, based on 69 solar scans obtained during two observational campaigns in 1993 and 1995. In both time intervals the He~I 1083 nm line was observed in absorption. The ratio of average intensity in the line and the average intensity of the nearby quasi-continuum was calculated and cautiously used as a measure of the line bsorption and represented as a function of position on the solar disc. Results indicate a distinct dependence of the He~I 1083 nm average relative line intensity on the solar latitude, its North--South asymmetry and well pronounced differences for the two campaigns belonging to different solar cycle phases. The latitudinal dependence is analysed with and without discriminating quiet Sun and active regions. The observed behaviour (the latitudinal dependence and a North--South asymmetry) is to a large extent a consequence of the presence/absence of active regions. The differences found for the two observing campaigns are not only due to decreased solar activity in 1995 as compared to 1993, but also due to different and much more pronounced telluric water-vapour contamination during the second observing interval. Finally, in the Appendix we describe all He scans used here in more detail and compare the numbers of solar features identified in other spectral regions along the scans for the two observational campaigns.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

POVEZANOST RADA