Authors: Samantha Wallace (NPP, NASA/GSFC), Nicholeen M. Viall (NASA/GSFC), C. Nick Arge (NASA/GSFC)

A fundamental aspect of solar wind formation is where the plasma originates from on the Sun. The solar wind originates from 3 types of coronal magnetic field – the continuously open fields that form coronal holes (CHs), or from either active region (AR) or quiet Sun (QS) at the magnetic open-closed boundary. Relating in situ solar wind observations to their source at the Sun is a critical step to understanding how the solar wind is formed, because the source determines the plasma temperature, its elemental composition, and the possible mechanisms involved in its release and acceleration. Recent missions enable more direct measurements of the pristine solar wind closer to its solar origin, however, the use of a model is required to bridge in situ solar wind observations to their precise source region observed remotely. In this work we use the Wang-Sheeley-Arge (WSA) model driven by Air Force Data Assimilative Photospheric Flux Transport (ADAPT) time-dependent photospheric field maps to connect the in situ observed solar wind at ACE, with its source region at 1 Rs. We classify the ACE-observed solar wind based on source region (CH, QS, or AR) using model parameters derived for the magnetic field lines connected to each source (e.g. spacecraft separation from the HCS and S-web arc, source region distance from magnetic open-closed boundary), and the corresponding photospheric field measurements at the source. We characterize the in situ properties of the solar wind observed at ACE (e.g. speed, proton density, nA/nP, Fe/O, carbon and oxygen charge state ratios) that originate from each source, in order to investigate whether the source region as defined here ultimately determines the plasma properties observed in situ. We use this methodology to investigate two Carrington rotations, one near solar maximum and one near solar minimum. We find a strong relationship between source region and charge state ratio observed in situ, and consistently low FIP in solar wind from coronal holes with widely varying FIP measurements from solar wind originating from the magnetic open-closed boundary. We discuss these results and other findings in the context of how the source region determines or influences the solar wind properties observed in situ. We conclude with future plans to expand this work to a larger statistical analysis over a solar cycle, and to statistically quantify the solar conditions that produce geoeffective ambient solar wind.