Testing MURaM and MPS-ATLAS against the quiet solar spectrum

Three-dimensional (3D) radiative magnetohydrodynamics (MHD) simulations are the only way to model stellar atmospheres without any ad hoc parameterisations. Several 3D radiative MHD codes have achieved good quantitative agreement with observables for our Sun. We aim to validate the most up-to-date version of the MURaM code against well established quiet Sun measurements, in particular spatially averaged measurements that are relevant for stellar studies. This validation extends the number of solar observables that MURaM can reproduce with high precision. It is also an essential condition for using MURaM to accurately calculate spectra of other cool stars. We simulate the solar upper convection zone and photosphere harbouring a small-scale-dynamo. Using time series of 3D snapshots we calculate the spectral irradiance, limb darkening and selected spectral lines, which we compare to observations. The computed observables agree well with the observations, in particular the limb darkening of the quiet Sun is reproduced remarkably well.