Results from the Spring 2025 Fast Wind Connection Science Campaign: Coordinated Sub-Alfvénic and Out-of-Ecliptic Observations

Parker Solar Probe and Solar Orbiter are revolutionising our understanding of the Sun’s corona and wind by providing an unprecedented multi-scale view of the inner heliosphere. The Fast Wind Connection Science Solar Orbiter Observing Plan (Fast Wind SOOP) in Spring 2025 highlighted the complementary nature of these missions. Following a Venus gravity assist in February 2025, Solar Orbiter increased its orbital inclination to begin investigating the Sun’s polar regions. In March 2025, with the Sun near activity maximum, Parker Solar Probe, Solar Orbiter, and near-Earth satellites intercepted fast solar wind (600-800 km/s) originating from a large trans-equatorial coronal hole within a few days of one another. Parker Solar Probe’s 24th perihelion sampled pristine, sub-Alfvénic solar wind around 10 solar radii, while Solar Orbiter conducted a latitudinal scan at 60–70 solar radii. The variation in radial distance and latitude between the two spacecraft provided valuable insight into the structuring of the solar wind at large scales. While Solar Orbiter targeted high resolution imaging and spectroscopy of the solar wind source regions, supported by observations from Hinode and IRIS. These coordinated campaigns are allowing us to investigate the physical process that heat, accelerate and structure the solar wind at both large and small scales.