  The aim of this paper is to try to explain the physical origin of the
non-thermal electron distribution that is able to form the enhanced intensities
of satellite lines in the X-ray line spectra observed during the impulsive
phases of some solar flares. Synthetic X-ray line spectra of the distributions
composed of the distribution of shock reflected electrons and the background
Maxwellian distribution are calculated in the approximation of non-Maxwellian
ionization, recombination, excitation and de-excitation rates. The distribution
of shock reflected electrons is determined analytically. We found that the
distribution of electrons reflected at the nearly-perpendicular shock
resembles, at its high-energy part, the so called n-distribution. Therefore it
could be able to explain the enhanced intensities of Si XIId satellite lines.
However, in the region immediately in front of the shock its effect is small
because electrons in background Maxwellian plasma are much more numerous there.
Therefore, we propose a model in which the shock reflected electrons propagate
to regions with smaller densities and different temperatures. Combining the
distribution of the shock-reflected electrons with the Maxwellian distribution
having different densities and temperatures we found that spectra with enhanced
intensities of the satellite lines are formed at low densities and temperatures
of the background plasma when the combined distribution is very similar to the
n-distribution also in its low-energy part. In these cases, the distribution of
the shock-reflected electrons controls the intensity ratio of the allowed Si
XIII and Si XIV lines to the Si XIId satellite lines. The high electron
densities of the background plasma reduce the effect of shock-reflected
electrons on the composed electron distribution function, which leads to the
Maxwellian spectra.
