Poster Abstracts

Name/Affiliation:  Colin Folsom (Institut de Recherche en Astrophysique et Planétologie)

Title:  The evolution of surface magnetic fields in young solar-type stars

The surface rotation rates of young solar-type stars decrease rapidly with age from the end of the pre-main sequence though the early main sequence. This suggests that there is also an important change in the dynamos operating in these stars, which should be observable in their surface magnetic fields. Here we present early results in a study aimed at observing the evolution of these magnetic fields through this critical time period. We are observing stars in open clusters and stellar associations to provide precise ages, and using Zeeman Doppler Imaging to characterize their complex magnetic fields. Results for ten stars, in four associations between 21 Myr and 125 Myr old, are presented. We find a trend towards weaker less dipolar magnetic fields with age, but no clear trends with rotation period. Observations are in progress to extend the sample to a wider range of ages and rotation periods.