We apply the theory of Melrose and Brown (1976), concerning the X-ray spectrum resulting from the combined precipitation and within-trap acceleration of non-thermal electrons, to the large solar flare of August 4, 1972, using high time resolution hard X-ray data from the ESRO TD-1A scintillation counter for the calculations. By so doing, we infer the time behavior of the electron source function Q(E, t), as a function of energy E and of the mean ambient trap density ri(cm-3).
We then interpret these results in the context of a variety of models: (i) a purely thick-target model; (ii) a static trap with continuous injection of fresh electrons; and (iii) a dynamic trap, with continuous redistribution of.electron energies due to, for example, modulations in the trapping magnetic field. It is concluded that there exists a minimum trap density/~crit below which the static trap description cannot be valid, but that ti </~crit is possible if a dynamic trap is invoked. Further, in such low density dynamic traps, the electron source function at a given instant may bear little or no resemblance to a power-law spectrum despite its production, via non-thermal bremsstrahlung, of a power-law X-ray spectrum.