Heavy Ion Properties as Diagnostics of Solar Wind Thermodynamic Evolution

Abundance ratios of heavy ions in the solar wind can be used to probe the low solar corona through the freeze-in and First Ionization Potential (FIP) effects, while their speeds and temperatures can probe both collisionless and collisional processes in the solar wind. We present results demonstrating how heavy ion properties act as diagnostics for phenomena spanning different regimes within the heliosphere. Through a cross-correlation analysis between heavy ion density ratios and proton specific entropy from 1998-2011, we find that the variability in solar wind fluid entropy freezes-in between approximately 1.4-1.8 solar radii in heliocentric distance, constraining time-dependent processes in solar wind formation. Additionally, by incorporating proton temperature anisotropies to compare with heavy ion temperatures, we observe that certain heavy ion species are less subject to the CGL conditions in the highly collisionless solar wind than protons are, placing constraints on inter-species energy partitioning. These analyses, based on measurements of heavy ions at 1 AU, can be extended to data collected by the Heavy Ion Sensor onboard Solar Orbiter. Through the incorporation of proton anisotropies and heavy ion measurements across variable heliocentric distances, these extended analyses will further probe the thermodynamic evolution of the solar wind.