Statistical Properties of Solar Wind and Interplanetary Magnetic Field Upstream of Planets at 1 au and Beyond: A Comprehensive Analysis

Abstract The solar wind and the interplanetary magnetic field (IMF) are of significant importance, as they affect the plasma environment and dynamic processes in the planetary magnetosphere. This study statistically analyzes the solar wind parameters upstream of Earth (ACE), Mars (MAVEN), Jupiter (Ulysses, Galileo, Juno), and Saturn (Cassini) and their solar activity phase (solar maximum, descending, minimum, and ascending phases) dependence. The heliolatitude variations are validated using Ulysses observations. Results show that the radial magnetic field decays more gradually than expected ( r −2 ), and the IMF intensity ( B ) decreases more rapidly at higher heliolatitudes. The solar wind proton density ( N p ) near Mars is significantly higher than expected, while the solar wind speed ( V ) is lower. The IMF spiral angle (SA) aligns well with the Parker SA upstream of planets and at high heliolatitudes, except for Mars. Martian anomalies may stem from mass loading by pickup ions (contributing to the increased N p and lower V ) and the IMF bending effect caused by Martian current systems. The B and solar wind dynamic pressure are higher during solar maximum compared to solar minimum. Additionally, the V , plasma beta, and Alfvén Mach number exhibit larger values during the solar descending phase compared to the solar ascending phase. The higher V results in a smaller IMF SA, and this effect is more pronounced near Earth and Mars but less noticeable near Jupiter and Saturn. Our statistical survey provides a reference for the upstream solar wind conditions at these planets, benefiting solar wind studies and planetary space environment research.