PARTICLE-ACCELERATION AND ENTROPY CONSIDERATIONS

Possible entropy constraints on particle acceleration spectra are disc ussed. Solar flare models invoke a variety of initial distributions of the primary energy release over the particles of the flare plasma - i e., the partition of the energy between thermal and nonthermal compone nts. It is suggested that, while this partition can take any value as far as energy is concerned, the entropy of a particle distribution may provide a useful measure of the likelihood of its being produced for a prescribed total energy. The Gibbs' entropy is calculated for severa l nonthermal isotropic distribution functions f, for a single particle species, and compared with that of a Maxwellian, all distributions ha ving the same total number and energy of particles. Speculations are m ade on the relevance of some of the results to the cosmic ray power-la w spectrum, on their relation to the observed frequency distribution o f nonthermal flare hard X-ray spectrum parameters and on the additiona l energy release required to achieve lower entropy fs.