We study the behaviour of three photospheric lines (Fe I 537.9, C I 538.0 and Ti II 538.1 nm), monitored on the Sun since 1978. The aim is to detect photospheric variations with the cycle. We reconstruct the cyclic variations of full-disk line depths as due to the active regions (ARs). We show that ARs alone cannot account all the observational results. The differences between observed behaviour and the AR contribution correlate with the measured center-disk line variations, and a common periodicity of ˜ 2.7 yr is present.
Line depth variations along the solar cycle: a biennial periodicity?
PIETROPAOLO, Ermanno;
2006-01-01
Abstract
We study the behaviour of three photospheric lines (Fe I 537.9, C I 538.0 and Ti II 538.1 nm), monitored on the Sun since 1978. The aim is to detect photospheric variations with the cycle. We reconstruct the cyclic variations of full-disk line depths as due to the active regions (ARs). We show that ARs alone cannot account all the observational results. The differences between observed behaviour and the AR contribution correlate with the measured center-disk line variations, and a common periodicity of ˜ 2.7 yr is present.File in questo prodotto:
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