Waves in stellar atmospheres

Theoretical models of intense magnetic flux tubes embedded in photospheres of late type stars are calculated. Magnetohydrodynamic waves generated in convective zones are radiatively damped in the lower part of the flux tube and next dissipated. In that way, the minimum temperature region and the lower part of chromosphere are formed. We discuss how the presence of flux tubes in stellar photospheres influences the temperature minimum and the chromospheric activity. Besides, we try to explain the fact that in some late type stars the strong chromospheric activity can exist. (author)