Backmapping of in situ data to their source surface. The empty circles show magnetic footpoints from PFSS extrapolation, color-coded with the identified solar wind region found in situ. The colored discs show the ballistic backmapping of Solar Orbiter in situ data during its encounter with the SIRs and HSSs, color-coded with the measured solar wind velocity. The velocity enhancements in the ballistically backmapped data correspond with HSS1 and HSS2. The black dotted line shows the position of the HCS, according to the PFSS solution.