Connecting Solar Orbiter and L1 Measurements of Mesoscale Solar Wind Structures to Their Coronal Source Using the ADAPT-WSA Model

Abstract Much of the dynamics of the ambient solar wind (SW) manifests at mesoscales—scales larger than kinetic but smaller than global structures. Mesoscale structures often form at the Sun, survive to 1 au, and are geoeffective. Identifying their origins, release, and acceleration mechanisms is critical to advancing heliophysics. We investigate a 6 day interval (2022 March 4 00:00:00 UT–2022 March 9 23:59:59 UT) in which Solar Orbiter (SO) was radially aligned with Earth. We characterize mesoscale structures observed in SO Heavy Ion Sensor (HIS) Fe/O and O 7+ /O 6+ in situ measurements, and confirm their survival to L1. A subset of these structures are periodic, suggesting that they formed at the Sun. We use the ADAPT-WSA model to connect in situ measurements to their remotely observed sources at the Sun. We characterize the SW sources using model-determined proxies for SW formation (e.g., the S-web). We compare Fe/O observed at SO/HIS, with S/O abundances derived by the Spectral Imaging of the Coronal Environment (SO/SPICE), at the WSA-determined SW sources. We find (1) SO and ACE/Wind observe similar many-hour structures, linking mesoscale structures from their source to two well-separated locations in situ for the first time. (2) Observed periodicities are consistent with those observed in prior studies of mesoscale structures throughout the inner heliosphere. (3) SW originating from only one of the four SPICE rasters can be interpreted as plasma originating from open fields. The SW from the other three require a different interpretation, and we suggest interchange reconnection as the most natural solution.