Cometary ions H₂O⁺ streamlines in the analysed simulations. A) Photoionisation only. B) Photoionisation + electron ionisation. C) Photoionisation + charge exchange. D) All processes. The colour code shows the bulk velocity of the cometary ions U_H2O⁺, ranging between 0 (blue) and 500 km s^-1 (red). The streamline tracing was performed by choosing equally-spaced seed points on the diagonal line between points of coordinate (x,y,z) = ( − 20,0, − 20) × 10³ km and (20,0,20) × 10³ km.