Three-dimensional structure of the coronal magnetic field and the solar wind speed distribution projected on the photosphere in 1974
Since the solar wind and coronal holes were relatively steady in 1974, the average distribution of the solar wind speed on the source surface and that of the line-of-sight component of the photospheric magnetic fields (B1) can be constructed, with fair accuracy, by the superposed epoch analysis. The three-dimensional structure of the coronal magnetic fields is then computed from this average map of B1 based on the potential model. The average distribution of the solar wind speed on the source surface, obtained from interplanetary scintillation observations, is then projected onto the photosphere along the open field lines in the corona. The high-speed regions thus projected are compared with the Hei (1083 nm) coronal holes and are found to have a similar geometry. The results are also suggestive that the solar wind does not blow out uniformly from the vicinity of a coronal hole and that the speed is higher at the east side in that region than at the west side. The slower speed regions on the source surface have a sinusoidal structure in heliographic latitude-longitude coordinates and are similar to the brightness distribution of the K corona and the structure of closed field line regions projected onto the photosphere.