Visualisation of simulation 1 (paraview) with additional annotations. The yellow-to-purple background is the plane containing the trajectory of BepiColombo during MSB1 (white line) on 1–2 October 2021, coloured according to plasma electron density n_e in cm⁻³. At the center, the sphere is coloured according to the radial magnetic field (negative in blue, positive in red), in normalised units. This is to show where the magnetic equator of Mercury is with respect to the plane containing the trajectory of the spacecraft. In the black frame, the magnetic field lines crossing the trajectory of BepiColombo are displayed in blue when they are connected on both sides to the planet, and in red when they are open planetary or solar wind magnetic field lines. The thick black dashed line stands for the bow shock, thin green dashed line stands for the magnetopause, and blue thick line stands for the boundary between closed and open field lines. Those boundaries delimit three regions: (1) the magnetosheath, (2) the magnetic cavity, and (3) the closed field lines region with a much higher electron density than in the magnetosheath (plasmasphere).