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Our study covers a comprehensive analysis of Interplanetary Coronal Mass Ejections (ICMEs) across a wide distance from 0.25-5.42 AU and temporal range from 1975-2022. Our primary focus is a statistical examination of a variety of physical parameters for the structures within ICMEs, specifically the sheath and magnetic obstacle (MO). Our methodological approach integrates data merging from 13 individual ICME catalogs into a unified catalog, facilitating a comprehensive evaluation of in-situ measurements obtained from diverse spacecraft. This approach offers an opportunity to discern variances across different solar cycles. Our empirical findings provide intriguing insights. Notably, MOs preceded by a sheath exhibit a marked increase in size upon reaching 1 AU from the Sun. Furthermore, both structures, MO and sheath, experience a strong increase in size around 0.75 AU, correlating with a decrease in the measured density at this distance. Moreover, our analysis reveals a shift in the spatial positioning of material accumulation proximate to the sheath interface. This transformation suggests a potential transition in the underlying mechanism governing sheath formation, indicating a shift from externally driven to internally accumulated material processes.
Larrodera et al. (Fri,) studied this question.