Calculated X-ray emission produced by LECR protons and α-particles interacting in a gas cloud of solar metallicity, for the differential injection rate of primary protons shown in Fig. 9. The contribution of accelerated α-particles is included as explained in the text, assuming in particular the solar abundance C_α / C_p = 0.0964. a) Λ = 10²¹ cm^-2; b) Λ = 10²⁴ cm^-2. IB: inverse bremsstrahlung; SEB: secondary electron bremsstrahlung. Photoelectric absorption is taken into account with a H column density of 10²² cm^-2.