Deriving the Coronal Separatrix‐Web With the WSA Model

We demonstrate a new capability of the Wang‐Sheeley‐Arge (WSA) model to routinely derive the coronal separatrix web (S‐web) as a standard data product. We describe our methodology for deriving the squashing factor () and we use Carrington rotation (CR) 2109 to illustrate the validation of our output with that derived from the POT3D model. We use the same CR to demonstrate a primary use case of our tool, namely, to interpret in situ observations based on their S‐web origin. We derive the ACE connectivity to the solar surface, and generate a time series that quantitatively relates the solar wind observed at ACE with derived at its source region. We demonstrate that all intervals of high , including one associated with a pseudostreamer, correlate with times when the charge state and abundance measurements at L1 are enhanced and highly structured. This has been predicted for solar wind originating from magnetic separatrix layers and quasi‐separatrix layers at the open‐closed boundary, where closed field plasma is released into the solar wind via interchange reconnection with open fields. Further, we relate to expansion factor () and coronal hole boundary distance (, DCHB), which are longstanding parameters used to empirically derive solar wind speed. We demonstrate that , though related to and DCHB, is a separate metric of the coronal magnetic field topology and a unique probe of solar wind formation. We conclude by highlighting the novel capabilities of this tool, and its future uses for space weather forecasting.