Trajectory (dashed-dotted black line) of the first BepiColombo flyby to Mercury in the X_MSO–ρ_MSO plane in units of the radius of Mercury, R_M = 2439.7 km (the black arrow marks the spacecraft direction). The red line corresponds to the time interval considered in this study corresponding to PICAM measurements and when BepiColombo sampled the solar wind near Mercury. The grey line represents the average bow shock surface (Slavin et al. 2009; Winslow et al. 2013). The inbound and outbound bow shock crossings are marked by blue text.