On an Estimate of the Dynamo-Generated Magnetic Fields in Late-Type Stars

The depth of the convection zone varies significantly with spectral type in late-type stars. We study the effect of this variation on the generation of magnetic fields by dynamo processes. For this we develop a scheme for determining the magnetic field strength generated in late-type main sequence stars. This method is based upon the assumption that the fields are determined when the rise time of a magnetic flux tube due to buoyancy is equal to the e-folding amplification time for the stellar dynamo. The basic results indicate that for a given rotational period, the magnetic field increases with (B-V) color, whereas the amplification time decreases, suggesting shorter cycle periods. For M stars and for rotational periods of the order of that of the Sun the magnetic field area coverage approaches 100% of the stellar surface, suggesting small dissipation scales for the magnetic field (flare stars).