Magnetic activity cycles in late-type stars

An intensive monitoring of the H and K Ca II lines for a large number of late-type stars, carried out since 1966 from Mount Wilson (US), has allowed the study of activity cycles in this kind of stars (Baliunas and Vaughan, 1985; Saar and Baliunas, 1992). About 30% of the monitored stars have clearly detected magnetic cycles, some of them showing more than one periodicity, the remaining objects having a chaotic or long trend behaviour. We present in this paper results from a model based on the dynamo action which attempts to reproduce the duration of the observed activity cycles and also link what the theory predicts on some quantities in the stellar interior, with observational results for the product f B, i.e. the mean magnetic flux at the stellar surface. © 1996 OPA (Overseas Publishers Association) Amsterdam B.V. Published in The Netherlands under license by Gordon and Breach Science Publishers SA.