The influence of turbulent pressure on the later stages of evolution of low- and intermediate-mass stars. (III). On the mechanism for driving strong stellar winds in red giant and AGB stars.

A criterion is presented for judging the occurrence or absence of dynamical instability in the convective envelope of a red giant or an AGB star. According to this criterion and the calculations for the evolution of 2.8 M_sun and 7 M_sun stars from the main sequence to the red giant stage and the AGB stage, it can be shown that the effect of turbulent pressure can cause a dynamical instability in the regions close to the surface of a red giant or an AGB star, leading to mass ejection outwards. This may be the mechanism for driving the strong stellar winds in red giants and AGB stars with very low surface temperature and feeble radiation pressure.