Overview of the HCS location and orientation. Bottom panel: map of the Sun’s source surface, at 2.5 R_⊙, with the red/blue contours showing open field lines with positive/negative polarity using an Air Force Data Assimilative Photospheric Flux Transport (ADAPT; Worden & Harvey 2000) magnetogram on June 1, 2020. The neutral line is shown as a solid black line, which is used as a proxy for the HCS. Overlain is a 6-h average of the in situ magnetic field data from Wind (lower) and Solar Orbiter (upper), mapped back to the source surface using a ballistic procedure. The color of these points represents the polarity, which has been defined as being within ±45° of the Parker spiral direction at each spacecraft. If the field direction lay outside this range then it has been not assigned a polarity (N/A). To signify changes in magnitude of the magnetic field B, the areal size of the points is proportional to B², normalized by the radial distance to the Sun. The two ICMEs can be seen at 220°, where the point size increases along with a change in magnetic polarity. On this plot the spacecraft travels from right to left. Top panel: solar wind speed measured by the Wind spacecraft, mapped back to the solar source surface. This reveals a positive polarity HSS between 150° and 200° longitude, preceded by a negative polarity slower plasma flow.