Dust formation in winds of long-period variables IV. Atmospheric dynamics and mass loss

We have calculated radiation-hydrodynamical models of the atmosphere and circumstellar dust shell ofC-rich longperiod variables which include a detailed description of the dust formation process. We discuss the time-dependent behaviour of the circumstellar envelope (e.g. multiperiodicity) and its relevance for observational properties like near-IR light curves and investigate the time-averagedmass loss characteristics of a sample of models satisfying radius–luminosity–mass and period– luminosity relations. The results can be summarized as follows: The dependence of the mass loss rate on stellar parameters predicts a strong increase of mass loss as stars evolve along the AGB. The models presented agree reasonably well with mean mass loss–period relations deduced from observations of Mira stars and the observed scatter of mass loss rates for a given period can be understood in terms of pulsation amplitude or nonlinearities of the wind mechanism. The wind velocities show a good correlation with the quantity (ρd/ρg)L?/M? which characterizes the strength of radiation pressure on dust relative to gravitation.