Left panel, upper plot: integrand of the specific emissivity, dε_ν∕dE, as a functionof the energy E, normalised to its maximum value and summed over the two polarisations (Eqs. (1)), computed at 100 MHz, 1 GHz, and 10 GHz (green, orange, and violet line, respectively), for B_⊥ = 2 μG. The coloured area below each curve corresponds to 95% of the total emissivity. Right plot: Same as the upper plot, as a function of the CRe spectral slope s. Main plot: Spectral slope as a function of the energy for the CRe spectrum by Orlando (2018; black solid line). Coloured lines show the range of energies (and the corresponding spectral slopes) contributing to 95% of the specific emissivity. Right panel: same as left panel, but for B_⊥ = 20 μG.