# Reconstructing coronal hole areas with EUHFORIA and adapted WSA model: optimising the model parameters **Authors:** Eleanna Asvestari, Stephan G. Heinemann, Mannuela Temmer, Jens, Pomoell, Emilia Kilpua, Jasmina Magdalenic, Stefaan Poedts arXiv: 1907.03337 ยท 2020-01-08 ## TL;DR This study compares EUHFORIA's WSA model with EUV observations to optimize model parameters, specifically the source surface and inner boundary heights, improving the accuracy of coronal hole area reconstructions. ## Contribution It systematically investigates the impact of source surface and inner boundary heights on coronal hole modeling, proposing optimized parameter ranges for better accuracy. ## Key findings - Default model heights are inadequate for accurate CH area modeling. - Lower heights for model boundaries improve the match with EUV observations. - 184 parameter combinations were tested to identify optimal model settings. ## Abstract The adopted WSA model embedded in EUHFORIA (EUropean Heliospheric FORecasting Information Asset) is compared to EUV observations. According to the standard paradigm coronal holes are sources of open flux thus we use remote sensing EUV observations and \textsc{catch} (Collection of Analysis Tools for Coronal Holes) to extract CH areas and compare them to the open flux areas modelled by EUHFORIA. From the adopted WSA model we employ only the Potential Field Source Surface (PFSS) model for the inner corona and the Schatten Current Sheet (SCS) model for the outer (PFSS+SCS). The height, $R_{\rm ss}$, of the outer boundary of the PFSS, known as the source surface, and the height, $R_{\rm i}$, of the inner boundary of the SCS are important parameters affecting the modelled CH areas. We investigate the impact the two model parameters can have in the modelled results. We vary $R_{\rm ss}$ within the interval [1.4, 3.2]$R_{\rm \odot}$ with a step of 0.1$R_{\rm \odot}$, and $R_{\rm i}$ within the interval [1.3, 2.8]$R_{\rm \odot}$ with the same step, and the condition that $R_{\rm i}