Authors: Aidan Nakhleh (University of Michigan), Nicholeen Viall (NASA Goddard), Sue Lepri (University of Michigan), Jim Raines (University of Michigan), Enrico Landi (University of Michigan)

The strong correlation between solar wind entropy and the frozen-in quantity O7+/O6+ indicates that entropy variability (i.e. structures in entropy time series data) is preserved from its solar source. This prompts the question: where in the corona is this entropy variability established? By cross-correlating solar wind proton specific entropy and properties of heavy ion distributions measured by the Advanced Composition Explorer from 1998-2011, we have found that entropy is not always strongly correlated with frozen-in properties. In particular, the weak correlation with C5+/C4+, which freezes in at lower coronal heights than O7+/O6+, C6+/C4+, and C6+/C5+, indicates that entropy variability must evolve above the C5+/C4+ freeze-in height. Similarly, a weak correlation between entropy and Fe/O, which traces chromospheric mass exchange with the corona on closed magnetic field lines, indicates that entropy variability continues to develop after field lines open. Together, these results suggest that the mechanisms generating entropy variability are active low in the corona and cease between 1.4-1.8 Rsun, corresponding to the transition from a collisional to collisionless plasma regime along open magnetic field lines.