Solar Flares

The Sun is an excellent laboratory for studying astrophysical particle acceleration. Particle acceleration is one of the principal channels of energy release in solar flares. Of all astrophysical sources, only for the Sun can the gamma ray emission produced and the particles that escape be simultaneously observed. A full understanding of the phenomenon, whether it is from particles continuously accelerated for hours or from particles accelerated in the impulsive phase and subsequently trapped in closed magnetic structure, is still not available.

A magnetic loop, or prominence on the Sun. When a loop hits another loop,the two combine to produce a solar flare.
This is a picture of magnetic loop, or prominence on the Sun. When a loops hit another loop, the two combine to produce a solar flare. Photo credit: Dr. Alan Title/Stanford Lockheed Institute for Space Research and NASA.

GLAST, with its higher sensitivity than EGRET, should observe a larger sample of G eV events and provide many more details. In particular, the extension of the spectrum to higher energies will determine the upper limit on the accelerated particle energy, and the higher sensitivity will reveal the structure of the time profiles, all of which should lead to a better understanding of the basics on the underlying processes. GLAST will still be operating as solar cycle 24 peaks near 2011. GLAST will therefore be available to complement other missions that are being planned to observe hard X-rays and nuclear gamma rays during that time period.