Total energy loss functions of primary and secondary CR particles k (protons, electrons and positrons, and photons), computed for a medium composition given in Table A.1 (L_k, thick black lines) and for atomic hydrogen (L_k,H, thin grey lines). Protons (upper panel): ionisation losses (short dashed lines) and pion production (dotted lines); the vertical dotted line shows the energy, E^as, at which the proton loss function changes its asymptotic behaviour from α = 1.28 to α = 1.08. Electrons and positrons (middle panel): ionisation losses (short dashed line), BS (long-dashed line), and synchrotron losses with the uncertainty on the magnetic field strength (shaded area, see Appendix A.2); the vertical dotted line shows the transition energy, E^syn, between BS (α = 1) and synchrotron (α = 2) losses. Photons (lower panel): photoionisation losses (dash-dotted line), Compton scattering (dotted line), and pair production (short-dashed line).