Coronal Models and Detection of Open Magnetic Field

Abstract: A plethora of coronal models, from empirical to more complex magnetohydrodynamic (MHD) ones, are being used for reconstructing the coronal magnetic field topology and estimating the open magnetic flux. However, no individual solution fully agrees with coronal hole observations and in situ measurements of open flux at 1~AU, as there is a strong deficit between model and observations contributing to the known problem of the missing open flux. In this paper we investigate the possible origin of the discrepancy between modeled and observed magnetic field topology by assessing the effect on the simulation output by the choice of the input boundary conditions and the simulation set up, including the choice of numerical schemes and the parameter initialization. In the frame of this work, we considered four potential field source surface based models and one fully MHD model, different types of global magnetic field maps and model initiation parameters. After assessing the model outputs using a variety of metrics, we conclude that they are highly comparable regardless of the differences set at initiation. When comparing all models to coronal hole boundaries extracted by extreme ultraviolet (EUV) filtergrams we find that they do not compare well. This miss-match between observed and modeled regions of open field is a candidate contributing to the open flux problem.