North-south motions in the solar wind

Abstract

Data supplied by the spacecraft Explorer 33, 34, and 35 and Pioneer 6 and 7 are used to perform a statistical study of the north-south component of the solar wind velocity. No evidence has been found for significant solar wind motions diverging away from the solar equator, such as those predicted by some models of the expanding corona. The north-south velocity appears to be strongly correlated with other solar wind parameters (density, bulk speed, proton thermal pressure); these relationships are interpreted in terms of high- and low-speed stream interactions, leading to the suggestion that most of the high-velocity streams in the period considered originated in the more active northern solar hemisphere. Although in general the meridional flow of the solar wind does not seem to be simply related to the pattern of the interplanetary magnetic field lines, a connection appears to exist in regions where the plasma is compressed, the lines of force (as well as the stream lines) being pushed away from the Parker spiral cone.