Temporal evolution of the mean temperature stratification from the two metal-poor ([Fe/H]  =  −3) turnoff-star surface convection simulations considered in Fig. 5. The curves show the differences of the mean temperature with respect to the standard case (self-consistent solution of the radiative transfer equation for a source function with a coherent scattering term) as a function of time. The total temporal coverage is 80 min, with snapshots taken every minute. Darker curves indicate later snapshots in the two sequences. Left panel: temporal evolution of the temperature differences for the simulation assuming a Planckian source function and no contribution of scattering to total extinction in optically thin layers. Right panel: corresponding evolution under the assumption of Planckian source function with scattering treated as true absorption.