Authors: Xiangyu Wu (MSSL, UCL), Christopher J. Owen (MSSL, UCL), Jesse Coburn (LPP), Georgios Nicolaou (MSSL, UCL), Daniel Verscharen (MSSL, UCL), Jingting Liu (MSSL, UCL), Yeimy J. Rivera (Center for Astrophysics | Harvard & Smithsonian), Stephanie L. Yardley (Northumbria University)

Whether solar-wind electrons retain information about their coronal source remains unresolved. The suprathermal strahl temperature has often been postulated as an indicator of source coronal electron temperature, while the core electron temperature has also been found to correlate with the solar wind velocity in the inner heliosphere. Using Solar Orbiter measurements at ∼0.5 au, we compare core and strahl temperatures derived from electron velocity distribution functions (eVDF) with heavy-ion charge-state ratios, which serve as proxies for the coronal electron temperature.

We present clear evidence, in several solar-wind streams, a proxy for the strahl parallel temperature correlates significantly and positively with the charge-state ratios O7+/O6+ and C6+/C5+. We find that, notably, the core perpendicular temperature (Tcore) also strongly correlates with the charge-state ratios. These results suggest that both thermal and suprathermal electrons can at times retain coronal information, but that aggregating multiple streams can obscure the underlying relationships. Overall, correlations at ~ 0.5 au are more evident than those typically reported at 1 au, while remaining weaker than those found closer to the Sun, consistent with progressive modification of the eVDF during solar-wind transport. Independently, DEM-weighted source-region temperatures also show a strong correlation with in-situ ​Tcore, further supporting a coronal thermal imprint in the core electron population.