Directionality of continuum gamma rays from solar flares

摘要

The hard X-ray spectrometer total counts are used as calibration to investigate how the brightness of gamma rays above 300 keV changes as a function of the heliocentric angle of a flare. The normalized gamma-ray brightness, on the average, increases with the heliocentric angle; a flare at the limb is estimated to be 13 times brighter in gamma-rays than a similar flare near the central meridian. Both pancake-like electron distributions and downward beam distributions can be adjusted to produce the deduced limb brightening.