Speaker
Description
Accurate modeling of the ambient solar wind, particularly high-speed streams (HSSs), is crucial as they drive geomagnetic activity and influence the propagation of coronal mass ejections through the heliosphere. Previous solar wind (SW) validation studies have reported discrepancies between modeled and observed SW conditions at L1, indicating that a major source of discrepancies arises from how we model the solar corona. Therefore, enhancing our predictive capabilities requires a thorough examination of coronal modeling approach. The Wang-Sheeley-Arge (WSA) model has been an extensively used workhorse model for providing near-Sun solar wind conditions. We thus present a detailed analysis of 15 different Carrington Rotations (CRs) to identify WSA model settings that result in successful and erroneous solar wind predictions at Earth. For the events studied, we find that increasing the grid resolution improves the open-closed boundary identification. This significantly improves predicting the onset and duration of HSSs. In addition, we find that an optimized source surface height (Rss) (lying between 1.8-3.1 Rsun) further enhances HSS prediction accuracy for the studied events. By investigating the physical implications of varying the Rss, we find that changes in Rss, (a) changes the open magnetic field footpoint to coronal hole boundary Great Circle Angular Distance (GCAD) maps (at the solar surface) of the associated coronal holes and (b) changes the foot-point locations of the magnetic connectivity to the sub-Earth locations. These factors change the near-Sun SW speed sampling, which eventually leads to differences in speeds near Earth. We also investigate the usefulness of coronal hole observations in constraining Rss and SW solutions at Earth, and highlight their underutilized value in guiding the selection of magnetic maps for improved ambient solar wind modeling at L1.
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