Effects of non-grey radiative transfer on 3D simulations of solar magneto-convection

We compare 3D simulations of photospheric magneto-convection which include a multigroup modelling of the non-grey radiative transfer with simulations based on a grey radiative transfer using the Rosseland mean opacity. While the simulation properties in the solar surface layers around tau(Ross) = 1 are very similar both cases, pronounced differences occur both in the temperature structure of magnetic field concentrations in the upper photosphere and in the appearance of strong magnetic fields in brightness maps. The results show that a non-grey treatment of the radiative transfer is mandatory if magneto-convective simulations are to be compared with observational results by calculating synthetic spectra of temperature-sensitive lines originating in the middle and upper photosphere.