EDP Sciences
Free access
Volume 374, Number 3, August II 2001
Page(s) 1100 - 1107
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20010780

A&A 374, 1100-1107 (2001)
DOI: 10.1051/0004-6361:20010780

Spectral analysis of solar diameter measurements recorded at Calern Observatory astrolabe during two solar cycles

R. Moussaoui1, A. Irbah1, E. Fossat2, J. Borgnino2, F. Laclare3, C. Delmas3 and F. X. Schmider2

1  CRAAG - Observatoire d'Alger, BP 63, Bouzaréah, Alger, Algeria
    e-mail: irbah@unice.fr
2  Université de Nice-Sophia Antipolis, UMR n$^{\circ}$ 6525 Astrophysique, Parc Valrose, 06108 Nice Cedex 2, France
3  Observatoire de la Côte d'Azur, Département CERGA, Avenue Copernic, 06130 Grasse, France

(Received 31 January 2000 / Accepted 3 May 2001 )

Solar diameter measurements performed with the Calern Observatory astrolabe (O.C.A - France) during more than two solar cycles show temporal variations. Due to the weather, seasonal effects and instrumental characteristics, recorded solar data are non uniformly sampled and present temporal gaps. Thus, to analyze these data, diameter measurements averaged over one or more months have generally been considered. This limits the accessible harmonic terms to a low frequency range. To determine short-term periodicities from the observed variations, all daily solar data need to be considered and also corrected from the zenithal distance. In the present work, we use two methods to analyze solar diameter measurements recorded at Calern Observatory astrolabe during the observation period 1975-1996. They are based on least square fits and deconvolution of the observation window function. Results deduced from the analysis confirm harmonic terms already found by other authors but also reveal new higher frequencies.

Key words: Sun: fundamental parameters -- Sun: oscillations -- methods: data analysis

Offprint request: J. Borgnino, borgnino@unice.fr

© ESO 2001