Chromospheric models of solar analogues with different activity levels

Abstract

We computed chromospheric models of the Sun as a star and of nine solar analogues. The atmospheric models were constructed to obtain the best possible match with the Ca II K and Hβ lines, including the asymmetry of the lines due to macroscopic velocity fields. The stars were chosen with 0.62 < B − V < 0.68 (the solar B − V = 0.65) and have a wide variety of magnetic activity levels, which allows us to study the differences in atmospheric structures induced by activity. For the less active stars we found that the changes with activity are in the region of the temperature minimum, while the most active stars show changes all along their atmospheric structures, mainly in the upper chromosphere. Regarding the macroscopic velocity fields, we can distinguish between the two groups. The most active group has a velocity field in the temperature-minimum region, and the other group in the chromospheric plateau. We also computed the net radiative losses for each model, and found that they depend linearly on the usual index of chromospheric activity, S CaII.