Investigation of Solar Wind Speed Characteristics Using IPS Observations and the PFSS+SCS Model

Understanding the relationship between solar wind speed and global coronal magnetic field is essential for space-weather forecasting and provides key diagnostics of the underlying acceleration mechanisms. Most observational studies to date have relied on near-ecliptic measurements dominated by slow wind, and the full range of wind speed, including fast wind, is insufficiently explored. Interplanetary scintillation (IPS) observations offer global coverage of wind speed; however, previous IPS-based studies have relied solely on the potential field source surface (PFSS) model, which does not adequately reproduce key features of the heliospheric magnetic field, potentially leading to the poor connectivity between the solar wind and its coronal source regions. Here we perform a comprehensive statistical analysis of the wind speed using IPS observations combined with PFSS and the Schatten current sheet (SCS) model. We find that the parameter f SS/B sun bifurcates the solar wind into two distinct groups: one showing a strong negative correlation and the other showing no correlation. This grouping is better organized by the footpoint magnetic field strength and the distance from coronal hole boundary (DCHB) than by solar magnetic activity, suggesting that the two groups may reflect fundamentally different acceleration mechanisms.