Top panel: thick lines show the profile of the narrow Balmer line for three cases: no CR acceleration (solid line) and acceleration efficiency (i.e. ϵ_CR = 22%) for two different values of the turbulent heating parameter, η_TH = 0 (dashed) and 0.4 (dot-dashed). For all the three cases the thin lines show the corresponding Gaussian having the same FWHM of the narrow Balmer line. Bottom panel: FWHM of the narrow Balmer line as a function of η_TH, for acceleration efficiency . For both panels the values of the other parameters are fixed as shown in the label of the bottom panel.