Calculated a) EW and b) luminosity of the 6.4 keV Fe Kα line produced by LECR electrons as a function of the path length of the primary electrons injected in the X-ray production region, for five values of the electron spectral index s (Eq. (A.7)). The ambient medium is assumed to have a solar composition and the electron minimum energy E_min = 100 keV. In panel b), the luminosity calculations are normalized to a total power of 1 erg s^-1 injected by the fast primary electrons in the ambient medium.