Time Histories of Gamma- and Hard X-Ray Emissions from Solar Flares

Abstract

The Hinotori gamma-ray spectrometer observed time histories of gamma-ray line and electron bremsstrahlung X-ray emissions from four solar flares. The time histories of impulsive flares require that both nuclei and electrons are rapidly accelerated to energies >10 MeV/nuc and >1 MeV respectively in a time scale of <10 s, and the gamma-ray line peak is coincident with the electron bremsstrahlung peak in <4 s. The gradual flare shows the gamma-ray line peak is apparently delayed by tens of seconds with respect to the electron bremsstrahlung peak. The gamma-ray line peak delay is attributed either to the simultaneous acceleration of nuclei and electrons in one step and a longer life time of the nuclei against the injection, the propagation and the slowing down in the flare region or to the second phase (step) acceleration of nuclei.