Altitude profiles of chemical production (solid lines) and loss (dashed lines) rates for four major ions in the nominal model: (a) O﹩{}_{2}^{+}﹩, (b) CO﹩{}_{2}^{+}﹩, (c) O⁺, and (d) NO⁺. Only reaction channels contributing more than 5% of the column-integrated total production/loss, or those that dominate within a specific altitude range, are displayed. The net contribution from vertical diffusion, which can act as both a source (solid black line) and a sink (dashed black line), is overlaid.