Total number of electrons above E_C, 20 keV and 50 keV (left to right) as a function of the power-law index of the initial electron distribution δ_b, obtained from the fitting of f_thick2.pro to the simulated footpoint X-ray spectra. The differently coloured lines indicate the different simulation setups used. The number of electrons are normalised by those from the fit to the beam-only (B, black line) X-ray spectrum.