Improvement to the global distribution of coronal plasma and magnetic field on the source surface using expansion factor fs and angular distance θb

Abstract

In this paper, we have developed an improved model to build a self-consistent global structure on the source surface of 2.5 Rs covering four different phases of solar activity. This model involves the topological effect of the magnetic field expansion factor fs and the minimum angular distance θb(at the photosphere) between an open field foot point and its nearest coronal hole boundary. The purpose of this effect is to separate the open field area and the close field area more effectively. The model uses as input for 136 Carrington Rotations (CRs) covering four different phases of solar activity: (1) an empirical model of the magnetic field topology on the source surface using Line-of-sight (los) photospheric field (Blos) measurements by Wilcox Solar Observatory (WSO); and (2) an empirically derived global coronal density distribution using K coronal polarized brightness (pB) by MKIII in High Altitude Observator (HAO). The solar wind speed on the source surface is specified by the function of both fs and θb, which are obtained by the magnetic field data. Then the coronal mass outputs are analyzed and the self-consistent global distribution on the source surface is numerically studied for the four different phases. Finally, the model estimates the solar wind speed at 1AU as a simple function of the speed on the source surface. Our numerical results indicate reasonable semi-quantitative agreement with observations at different phases of solar activity.