X-Ray, Radio and SEP Observations of Relativistic Gamma-Ray Events

The rather frequent occurrence, and sometimes long duration, of -

ray events at photon energies above 100 MeV challenges our understanding of

particle acceleration processes at the Sun. The emission is ascribed to pion-decay

photons due to protons with energies above 300 MeV.We study the X-ray and radio

emissions and the solar energetic particles (SEPs) in space for a set of 25 Fermi

-ray events. They are accompanied by strong SEP events, including, in most cases

where the parent activity is well-connected, protons above 300 MeV. Signatures of

energetic electron acceleration in the corona accompany the impulsive and early

post-impulsive -ray emission. -ray emission lasting several hours accompanies

in general the decay phase of long-lasting soft X-ray bursts and decametric-tokilometric

type II bursts. We discuss the impact of these results on the origin of

the -ray events.