Intensity (in arbitrary units) of the HXR emission spectra calculated from Eq. (7) for different energies, models and propagation directions (0 to 90° for downwards emission and from 90° to 180° for upwards emission). Dash-dotted line: emission from upwards propagating particles; dotted line: from downwards propagating particles, dashed line: total emission (downwards + upwards); solid line: observational data multiplied by the corresponding factors to match the simulated absolute intensities.