The determination and use of mean electron flux spectra in solar flares

Hard X-ray spectra in solar flares provide information on electron acceleration and propagation processes. We here point out that the inference of these processes involves two distinct steps: (1) the model-independent deconvolution of the hard X-ray spectrum to obtain the effective mean electron spectrum (F) over bar (E) in the source and (2) the model-dependent interpretation of this mean spectrum in terms of physical processes operating in that source. Thus, the mean electron spectrum is a natural "middle ground" on which to compare the predictions of models with observations, and we urge the presentation of results, both from analysis of photon spectra and from modeling of candidate physical processes, in the form of (F) over bar (E) spectra. We consider the constraints that various source models impose on (F) over bar (E), and we present explicit forms for an illustrative (F) over bar (E) corresponding to the injection of a power-law spectrum of electrons into a thick target with a nonuniform ionization level.