Solar dynamo cycle variations with a rotational period

TL;DR

This study uses non-linear mean-field dynamo models to analyze how solar-like magnetic cycle parameters vary with stellar rotation periods from 1 to 30 days, revealing different behaviors in kinematic and non-kinematic models.

Contribution

It provides a comparative analysis of kinematic and non-kinematic dynamo models, highlighting their different predictions for magnetic cycle variations with stellar rotation.

Findings

Magnetic cycle period decreases with faster rotation in kinematic models.

Non-kinematic models show non-monotonic cycle period variation with rotation.

Magnetic flux growth and saturation occur at very rapid rotation periods.

Abstract

Using the non-linear mean-field dynamo models we calculate the magnetic cycle parameters, like the dynamo cycle period, the amplitude of the total magnetic energy, and the Poynting flux luminosity from the surface for the solar analogs with rotation periods of range from 1 to 30 days. We do simulations both for the kinematic and non-kinematic dynamo models. The kinematic dynamo models, which take into account the non-linear $\alpha$-effect and the loss of the magnetic flux due to magnetic buoyancy, show a decrease of the magnetic cycle with the decrease of the stellar rotation period. The stars with a rotational period of less than 10 days show the non-stationary long-term variations of the magnetic activity. The non-kinematic dynamo models take into account the magnetic field feedback on the large-scale flow and heat transport inside the convection zone. They show the non-monotonic variation of the dynamo period with the rotation rate. The models for the rotational periods fewer than 10 days show the non-stationary evolution with a slight increase in the primary dynamo period with the increase of the rotation rate. The non-kinematic models show the growth of the dynamo generated magnetic flux with the increase of the rotation rate. There is a dynamo saturation for the star rotating with a period of two days and less. The saturation of the magnetic activity parameters is accompanied by depression of the differential rotation.