Interpretation of the 1991 June 11 High Energy Solar Flare

The X12+ solar flare on 1991 June 11 is interpreted in the context of multiple stages of particle acceleration. The June 11 flare is arguably the archetypical Long Duration Gamma Ray Flare. Over the course of more than eight hours at gamma-ray energies, it exhibited intense impulsive behavior, followed by a quiet period of several minutes, then followed by an even higher-energy phase, settling into a stationary gamma-ray spectrum extending well above 100 MeV. This phase lasted for several hours. The flare was well observed by the Compton Observatory. The distinct phases and the evolving spectrum demand separate phases of particle acceleration. We have performed broad band analysis of the spectrum for different phases and transitions and interpret the spectrum and temporal behavior in terms of an intense impulsive phase followed by a leaky box acceleration phase. The spectrum and the time scales are interpreted in terms of the physical parameters present in the corona.