The gas density (orange with units on the left y-axis) and the CR proton flux Φ_p(x) (units on the right y-axis) are plotted along the los in the direction specified by the Galactic longitude and latitude (l,b) = (−120°,−10°). The three models of Table 1 have been considered for the calculation of the proton flux. They lead to the blue (Min), red (Med) and green (Max) curves. As an illustration, the CR proton total energy E_p = m_p + T has been set equal to 30 GeV. The relative distribution of primary nuclei along the los is not expected to change much with energy.