The global nature of solar cycle variations of the solar wind dynamic pressure

Abstract

The solar wind dynamic pressure measured near the ecliptic varies over the solar cycle. A major unanswered question has been whether this variation is a global feature or restricted to low latitudes and thus perhaps a consequence of the changing heliospheric current sheet configuration. We use plasma data from IMP-8, Ulysses and Voyager 2 to show that the large-scale variation of the solar wind dynamic pressure is the same at all latitudes. Thus the solar wind source varies globally over the solar cycle, with important implications for the source mechanism and motions of the heliospheric boundaries.