Fraction of H₂O⁺ cometary ions (density ratios) created by A) photoionisation, B) electron ionisation and C) charge exchange in the analysed simulations. Density ratios, expressed in %, are calculated as with j ∈ [PI, EI, CX], for photoionisation, electron ionisation and charge exchange, respectively. The position of the comet nucleus at coordinates (x,y,z) = (0,0,0) is shown by a black cross. The white dotted box is the area zoomed-in in Fig. 9.