Cosmic flare transients - Constraints upon models for energy storage and release derived from the event frequency distribution

Abstract

Flare behavior for a variety of transient sources, including the Sun, flare stars, and a transient cosmic X-ray source, is examined. It is found that, although these sources span an energy release rate of over 10 decades, the flare frequency (v) as a function of energy released (E) follows a similar power law [v(E) E - J at large energies for all these sources; the flare frequency distributions at low energies, however, differ substantially. This result is used to develop a model for the general flaring phenomenon which allows a unified description of the flaring process for these diverse sources and which permits one to infer information concerning the modes of energy storage and release; specifically, the power-law behavior is shown to follow from the assumption that flaring is a stochastic relaxation phenomenon and from the requirements that the e-folding time for energy storage be constant (independent of the instantaneous free energy accumulated) and that the energy released be large when compared with the energy of the unperturbed state. These requirements place constraints upon physical models for transient sources in addition to those adduced from the spectral behavior of the transient itself. Subject headings: plasmas - stars: flare - Sun: flares - X-rays: bursts