Variations in the γ-ray flux relative to the reference case of Fig. 4. The red line is obtained when all the propagation parameters are extracted from the Med set of Table 1. Left panel: changing only the normalization K₀ of the space diffusion coefficient from its Med value to the lowest (1.6 × 10^-3 kpc²/Myr) and highest (7.65 × 10^-2 kpc²/Myr) values allowed by the B/C analysis yields the blue and green curves respectively. Right panel: same as in the left panel but varying the spectral index δ instead of the normalization K₀. The blue and green curves are derived from the smallest (0.46) and largest (0.85) values of the spectral index respectively.