Le séminaire a lieu le jeudi 10 novembre 2005 de 14h300
à
15h30
dans la salle de réunion
du PHC (Observatoire de Nice).
The full sets of daily magnetograms from Mount Wilson (about 55,000 magnetograms 1966-2004)
and from Kitt Peak (about 7,700 magnetograms 1974-2000) have been
analysed to explore the variation of the magnetic pattern on time scales from
the 22 yr Hale cycle to the rotational time scale. Various forms of time series
and pattern analysis have been used, including Fourier transforms, wavelet
periodograms, and spherical harmonic decomposition. A large number of
quasi-periodicities with limited coherence lengths have been found, which will
be shown and discussed in this talk.