Talk

Differential rotation, meridional circulation, and cycle perids for early M dwarfs

Manfred Küker, Leibniz-Institut für Astrophysik Potsdam

Recent observations find two characteristic cycle times for early-type M stars dependent on the rotation period. They are of order one year for fast rotators (Prot < 1 day) and of order four years for slower rotators. Additionally, the equator-to-pole differences of the rotation rates are known from Kepler data for the rapidly rotating stars and are well reproduced by mean field theory. The resulting amplitudes of the meridional circulation allow the calculation of the travel time from pole to equator at the base of the convection zone. These travel times strongly increase with rotation period and always exceed the observed cycle periods. A flux transport dynamo in early M dwarfs is thus not supported by our model and the data.