Solar cycle dependence of the solar wind dynamics: Pioneer Voyager, and Ulysses from 1 to 5 AU

Significant differences between Pioneer and Voyager observations were found in solar wind structure between 1 and 6 AU. These disagreements were attributed to temporal effects related to the solar cycle, but no unifying study of Pioneer-Voyager observations was performed. On the basis of maps of large-scale features we unify previous reports of Pioneers 10 and 11, Voyagers 1 and 2, and Ulysses observations from 1 to 5 AU. The five spacecraft traveled from Earth to Jupiter at different phases of the solar sunspot cycle. We compare the observations of solar wind streams, interplanetary shock waves, interaction regions, and magnetic sectors. We find that solar wind dynamics has a very irregular behavior throughout the solar cycle. There are continual transitions between periods of a few solar rotations dominated by slow solar wind, transient events, and irregular patterns of magnetic sectors; and periods of a few solar rotations dominated by interaction regions and well-defined magnetic sectors. These transitions occur at temporal scales of the order of 2-4 solar rotations. It is suggested that these transitions are associated with changes in coronal holes and might be related to the yearly modulation of solar wind speeds. The five spacecraft observed, on average, about 3 to 4 interplanetary shocks per solar rotation period. The 90 percent of the total number of shocks detected by Pioneer 11 were caused by interaction regions. However, between 40 to 55 percent of the total number of shocks detected by the other spacecraft were transient forward shocks. The expansion rate of the CIRs between 1 to 5 AU is about 94 km/s, however, there is a significant diversity in the characteristics of the interaction regions.