A new look at dynamo cycle amplitudes

Abstract

We explore the dependence of the amplitude of stellar dynamo cycle variability (as seen in the Mount Wilson Ca II HK timeseries data) on other stellar parameters. We find that the fractional cycle amplitude A_cyc (i.e. the ratio of the peak-to-peak variation to the average) decreases somewhat with mean activity, increases with decreasing effective temperature, but is not correlated with inverse Rossby number Ro^{-1}. We find that A_cyc increases with the ratio of cycle and rotational frequencies omega_cyc/Omega along two, nearly parallel branches.