Speaker
Description
Stellar magnetic activity, manifested in spots, faculae, and brightness variability, depends sensitively on fundamental parameters such as stellar mass, age, rotation, and metallicity. Understanding how these factors shape active regions is essential not only for interpreting other stars, but also for placing the Sun into its proper stellar context.
Three-dimensional radiative magnetohydrodynamic (MHD) simulations of the solar photosphere now provide a realistic framework for modelling magnetoconvection and emergent intensity contrasts. The next step is to extend this physically consistent approach beyond the Sun. In this talk, I present a grid of 3D radiative MHD models spanning F, G, K, and M stars, enabling a systematic comparison of active-region properties along the main sequence.
The models reveal clear departures from what is observed on the Sun. Facular regions, bright in the solar case, progressively lose contrast towards cooler effective temperatures and become dark from approximately spectral type M2 onwards. In addition, metallicity significantly modulates radiative contrasts, with enhanced metallicity favouring darker facular signatures even at otherwise solar parameters. These results demonstrate that magnetic activity cannot be interpreted solely through a solar lens: stellar type and composition fundamentally reshape the observable manifestations of active regions.