Relationship of ICME Composition Signatures with Solar Activity during 2009–2025
Аннотация
Abstract Coronal Mass Ejections (CMEs) are among the most energetic solar eruptions, expelling magnetized plasma from the corona into interplanetary space. Their interplanetary counterparts, known as Interplanetary Coronal Mass Ejections (ICMEs), retain distinct compositional signatures that reflect the physical conditions of their solar source regions. This study presents a statistical analysis of ICME composition dependence on solar activity during 2009–2025, covering Solar Cycle (SC) 24 and the ascending phase of SC 25 through its maximum, and compares the results with SC 23 studied by Song et al. (2021). Using data from the Solar Wind Ion Composition Spectrometer (SWICS) aboard the Advanced Composition Explorer (ACE), we examined the average iron charge state (⟨QFe⟩), ionic ratios (C6+/C5+ and O7+/O6+), and the elemental abundance ratio (Fe/O) for 307 ICMEs listed in the Richardson and Cane ICME catalog. The results show strong positive correlations of ⟨QFe⟩ (r = 0.86) and O7+/O6+ (r = 0.85) with the annual sunspot number (SSN), whereas C6+/C5+ exhibits a weak correlation (r = 0.17) primarily due to SWICS 2.0 upper-end saturation truncation that suppresses the solar maximum signal, and Fe/O a moderate correlation (r = 0.57). The Fe/O ratio, a proxy for the First Ionization Potential (FIP) effect, displayed elevated values during the maxima of both SC 24 and SC 25, suggesting enhanced elemental fractionation during periods of increased magnetic activity. Comparing with SC 23, we find that the overall solar cycle dependence of ICME composition persists across cycles, though with notable quantitative differences attributed to the different magnetic activity levels between cycles. These findings confirm that ICME compositional signatures are strongly modulated by the solar cycle, offering insights into CME initiation, coronal plasma processes, and their implications for space weather forecasting.