Vertical column density profiles for HCO⁺ and N₂H⁺ for our model series (Table 5). The left column shows the models with the ISM like CRs (ζ_CR ≈ 2 × 10^-17 s^-1), the right column with low CRs (ζ_CR ≈ 2 × 10^-19 s^-1). The top row shows HCO⁺, the bottom row N₂H⁺. The blue lines are for models with, the red lines are for models without SPs. Dashed (solid) lines are for models with high (normal) X-rays. The orange solid line shows the Turner model. The grey shaded area marks a difference of a factor 3 in the column densities relative to the CI_XN (ISM CR, normal X-rays) and CL_XN model (low CR, normal X-rays), respectively.