Constraining Global Coronal Models with Multiple Independent Observables

Abstract:

Global coronal models seek to produce an accurate physical representation of the Sun's atmosphere which can be used to probe the dominant plasma physics processes, to connect remote and in situ observations and operationally to predict space weather events which can impact the Earth. Assessing their accuracy and usefulness is a complex task and there are multiple observational pathways to provide constraints on such models and tune their input parameters. In this work, we aim to combine several such independent constraints in a systematic fashion on coronal models. We study the intervals of Parker Solar Probe's early solar encounters to leverage the unique in situ observations taken close to the Sun, and the wealth of supporting observations and prior work analyzing these time intervals. We require our coronal models to predict the distribution of coronal holes on the solar surface, and the neutral line topology. We compare these predictions to (1) direct Extreme Ultraviolet (EUV) observations of coronal hole locations, (2) white light Carrington maps of the probable neutral line location at a few solar radii, (3) the magnetic sector structure measured in situ by Parker Solar Probe as well as 1AU assets. For each of these constraints we compute a simple metric to evaluate model agreement and compare and contrast these metrics to evaluate and rank the overall accuracy of the models over a range of input parameters. Initial results using the coronal hole metric to analyze Potential Field Source Surface (PFSS) models indicate the optimum source surface height (Rss) parameter varied from encounter to encounter. Rss = 1.5 - 2.0 R_sun is shown to work best for Encounters 1 and 3, but higher (2.0-2.5 R_sun) for encounter 2, in agreement with the magnetic sector structure metric and previous work (e.g. Panasenco et al. 2020). We discuss the extension of these results to all three metrics, assess differences in model accuracy among input photospheric boundary conditions and investigate models with more physics than PFSS.