Strength of the self-generated UV radiation field (top panel) and ionization rate of hydrogen induced by the self-generated EUV and X-ray radiation field (bottom panel) in the radiative precursor, at z = 0. Both quantities are shown as functions of the shock velocity for different values of the preshock density and for B₀ = 1 μG. The strength of the UV radiation field is calculated from the integral of $I_{\nu }^{\text{int }}$, over solid angle and frequency between 911 and 2400 Å, normalized to the value obtained by Mathis (Mathis et al. 1983). The strength of the external UV radiation field used in this work (G₀ = 1) is shown as a gray line on the top panel. The cosmic ray ionization rate of atomic hydrogen used in this work $({\zeta }_{\mathrm{H}}={\zeta }_{{\mathrm{H}}_2}/2.3=1.3\times {10}^{-16}{\mathrm{s}}^{-1})$ is shown as a gray line on the bottom panel.