Solar wind and interplanetary shock parameters near Saturn's orbit (∼10 AU)

Abstract

In this work, in-situ 1-h averaged plasma and magnetic field spacecraft data are used to characterize solar wind conditions near Saturn's orbit. Further, high resolution solar wind interplanetary data are used to identify and to calculate interplanetary shock parameters. When only plasma or magnetic field data are available, identified discontinuities were classified as possible shocks. Solar wind parameters at 10 AU decrease as expected from the inner heliosphere averages. For instance, solar wind dynamic pressure is ∼2% and ∼40% of its value at 1 and 5 AU, respectively. Wave magnetosonic speed is similar to 5 AU, but it is only about 60% of the 1 AU value. From analysis of high resolution plasma and magnetic field data, only a small number of shocks (13) were identified, because of scarce data availability. On the other hand, a larger number of possible shocks (60) were identified. Most of the confirmed shocks (∼75%) were fast forward shocks, while ∼25% were reverse shocks. Mach numbers ranged from 1.2 to 3.5 (average 2.2). Shock normal angle was on average 68° with oblique to perpendicular propagation to the magnetic field. From solar wind and interplanetary shock parameters analyzed in this work, and comparison with results from other works at different radial distances, it is concluded that conditions for shock occurrence and shock strength seem to increase from 1 to 5 AU and then level off or decrease near ∼10 AU, with shock strength at 10 AU comparable to shock strength at 1 AU. These results are of interest for interplanetary dynamics and for solar wind-planetary magnetosphere coupling.