A Comparative Study of Different Approaches to Modeling the Solar Wind

The Wang-Sheeley-Arge (WSA) model is regularly used to predict the background solar wind speed and the interplanetary magnetic field (IMF) polarity from photospheric observation. The predictions near the sun are made from an empirical formula which has two parameters: (1) the magnetic expansion factor and (2) the minimum angular distance from a field line foot point to the edge of the coronal hole. A kinetic propagation model is then used to determine the values at 1AU. In this paper, we address that two factors can affect the result to a significant extent: (1) treatment of input data and (2) the algorithm used to compute the two parameters. We study the model dependence of the prediction and try to optimize the method with different approaches. Three different models (potential field source surface (PFSS) model, Schatten current sheet (SCS) model integrated with PFSS, and horizontal-current current-sheet source-surface (HCCSSS) model) are discussed here. The predictions perform variously in different phases of the solar cycle, with SCS generally gives a better prediction