Variations of Heavy Ions in Interplanetary Shock Driven by Interplanetary Coronal Mass Ejections and Stream Interaction Regions

Abstract

In the solar wind, the fluctuation of heavy ion abundance serves as a crucial physical metric. This not only mirrors the attributes of the solar wind’s originating solar region but also signifies its influence on Earth’s magnetosphere. Utilizing data from the Advanced Composition Explorer satellite, this investigation scrutinizes heavy ion variations in stream interaction region (SIR)- and interplanetary coronal mass ejection (ICME)-driven shocks. We further delineate the disparities in heavy ion fluctuations between these two types of interplanetary shocks across diverse solar activity cycles. Our findings reveal that ICME-driven shocks typically manifest elevated shock velocities and magnetic field strengths relative to their SIR-driven counterparts. Additionally, heavy ion abundance ratios, such as C6+/O4+, O7+/O6+, He/O, Si/O, and Fe/O, are consistently higher in ICME-driven shocks than in SIR-driven shocks. During varying solar activity cycles, these ratios surge postarrival of ICME-driven shocks. At solar maximum, these elevated ratios persist, whereas they revert to baseline levels swiftly during solar minimum. For SIR-driven shocks, the alteration in heavy ion abundance ratios is comparatively subdued, yet a noteworthy correlation with the solar activity cycle is evident.