Testing MURaM and MPS-ATLAS against the quiet solar spectrum

Abstract

Context. Three-dimensional (3D) radiative magnetohydrodynamic (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. Aims. We aim to validate the most recent version of the MURaM code by comparing MURaM results to well-established quiet-Sun measurements, in particular spatially averaged measurements that are relevant for stellar studies. This extends the number of solar observables that MURaM can reproduce with high precision. Our validation is an essential condition to ensure that MURaM can be used to accurately calculate the spectra of other cool stars. Methods. We simulated the solar photosphere and upper convection zone, which harbours a small-scale-dynamo. Using time series of 3D snapshots, we calculated the spectral irradiance, limb darkening, and selected spectral lines, which we compared to observations. Results. The computed observables agree well with the observations; in particular, the limb darkening of the quiet Sun is reproduced remarkably well.