Dimensionless ion number density profile versus scaled cometocentric distance as a function of α with τ_c = 0 (left panel) and τ_c = 3 (right panel). On the y-axis, the values of the ion number density n_i are scaled with respect to the maximum ion number density reached when only transport is considered for a given ion, i.e. . As (coloured curves) increases, more and more ion-neutral reactions take place especially close tothe nucleus. This results in damping the number density of ions reacting with H₂ O.