2001A&A...369..222K

We computed models of a three-component nonisothermal radiatively driven stellar wind for different spectral types of hot B stars. We showed that friction heats mainly the outer parts of the wind and the modified temperature stratification leads to a decrease of the outflow velocity. Contrary to the isothermal case, even the possibility of decoupling of radiatively absorbing ions and (major) nonabsorbing component is excluded for a realistic form of the driving force. Regardless of the actual form of the driving force, we derived general conditions under which decoupling of a stellar wind may occur. We demonstrated that the possibility of decoupling is closely related to the functional dependence of the driving force and to the ratio of the densities of individual components. We discuss several consequences of a multifluid phenomenon in hot star winds, particularly metallicity effects and the implications of possible helium decoupling on chemically peculiar stars. We propose an explanation of the low terminal velocity of τ Sco based on frictional heating.