NLTE-problem solution for MgI in the M-giant atmosphere with a chromosphere

Source functions and theoretical MgI line profiles in the M-giant atmosphere (Teff=3800 K, lg g=1.5) have been calculated. The M-giant atmosphere models with chromospheres which have different temperature minimum locations have been empirically constructed. A conclusion is drawn that the shape of the MgI intercombinate line λ 457.11 nm demonstrates a marked dependence on the temperaure distribution in the stellar atmosphere. At the same time strong subordinate Mg I lines are not sensitive to the outer layer structure of the red giant atmosphere