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Astron. Astrophys. 323, 151-157 (1997)

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On the cycle periods of stellar dynamos

A.J.H. Ossendrijver

SRON Laboratorium voor Ruimteonderzoek, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

Received 11 June 1996 / Accepted 6 December 1996


We show that the cycle periods ([FORMULA]) of slowly rotating lower main-sequence stars with well-defined periodic chromospheric activity can be parametrized by the rotation period [FORMULA] and the convective turnover time [FORMULA] through a relation of the form [FORMULA], with [FORMULA] and [FORMULA]. This suggests a common dynamo mechanism for slowly rotating stars lower main-sequence stars. Using a simple linear mean-field dynamo model, we are able to reproduce the observed relation if [FORMULA], the total difference in angular velocity along the radial direction, scales as [FORMULA] with [FORMULA], and if the [FORMULA] -coefficient scales as [FORMULA] with [FORMULA]. This would suggest that, with increasing rotation rate, differential rotation decreases while [FORMULA] rapidly increases.

Key words: stars: magnetic fields – stars: activity – stars: late-type – MHD

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998