Solar-cycle variations of interaction regions: in-ecliptic observations from 1 to 5 AU

Abstract

We study a combined set of 97 interaction regions detected by Pioneers 10 and 11, Voyagers 1 and 2, and Ulysses from 1 to 5 AU during their respective journeys to Jupiter at different phases of the solar cycle. The fast streams associated with the IRs detected by Voyager were slower than the fast streams detected by Pioneer and Ulysses. The comparison between the latitudinal tilts of the IRs detected by Voyager and Ulysses and the tilts of the current sheets show a qualitative agreement with the predictions of heliocentric evolution by numerical simulations of tilted interaction regions. The interaction regions detected by the Pioneers tend to be thinner than the interaction regions detected by Voyagers and Ulysses in the same heliocentric range.