Late-type dwarfs logR'HK and magnetic fields

We also combine our results with archival chromospheric activity data and published observations of large-scale magnetic field geometries derived using Zeeman-Doppler Imaging. The chromospheric activity data indicate a slight under-density of late-F to early-K stars with -4.75<=logR'HK<=-4.5 . This is not as prominent as the original Vaughan-Preston gap, and we do not detect similar under-populated regions in the distributions of the mean |Bl|, or the Bl and logR'HK variability amplitudes.

Chromospheric activity, activity variability, and toroidal field strength decrease on the main sequence as rotation slows. For G stars, the disappearance of dominant toroidal fields occurs at a similar chromospheric activity level as the change in the relationships between chromospheric activity, activity variability, and mean field strength.