A) Magnetosonic Mach number M_ms and B) plasma β in the x − y (top) and x − z (bottom) planes for the hybrid simulation, with all processes (photoionisation, electron ionisation and charge exchange) included. The 3D bow shock surface fitted for M_ms = 2 in panel A is shown as a transparent meshed surface enveloping the inner plasma regions, the outer surface of which is delimited as a black line. The vertical dashed lines mark the subsolar (or standoff) position of the bow shock, R_bs = 6570 km (see text for explanation). The Sun is situated on the + x axis, with the solar wind propagating to − x at velocity . Because the undisturbed interplanetary magnetic field is directed along + y, the undisturbed convection electric field E^sw = − U^sw × B^sw is in the x − z plane. The position of the comet nucleus at coordinates (x,y,z) = (0,0,0) is shown by a cross.