Profiles of averaged temperature versus the optical depth for fine-tune models. The temperature is averaged between the optical depth given by the coordinate of the horizontal axis and the surface of the corona. Thicker lines are overlayed to indicate where the condition for the TI is fulfilled. Circle markers are temperatures and optical depths obtained by Jin et al. (2012). Cross markers indicate the averaged temperature at τ_cor of a given model. Magnetic parameters are adjusted so that the temperature profile crosses the observational point. Each profile is shifted slightly for a clearer presentation and models are sorted according to the accretion rate, ṁ.