Unusual Time History of Hard X-Ray and Gamma-Ray Emissions from the 1981 April 4 Flare

Abstract

The Hinotori satellite observed an unusual time history of hard X-ray and gamma-ray emissions from a limb flare on 4 April, 1981. The detailed comparison of the time history reveals that the gamma-ray emission precedes the hard X-ray emission by about 10 s. Following three possibilities are suggested to explain the unusual time history: (1) The ion acceleration precedes the electron acceleration, (2) the ions and electrons are simultaneously accelerated, but the nuclear reactions responsible for gamma-ray emission precede the electron bremsstrahlung responsible for hard X-ray emission, and (3) the gamma-rays and hard X-rays are simultaneously emitted, but the hard X-rays are strongly attenuated from the limb effect.