Gamma-ray emission and particle acceleration mechanisms of solar flares

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Since the launch in 2008, Fermi-LAT has detected a lot of solar flare gamma-rays over several tens of events. The MeV/GeV gamma-ray spectra showed clear and significant turnover at several hundreds of MeV, indicating that the gamma-rays are produced via pion-decay process. The large photon statistics allowed us to pin-down the location of the emission region and we found that the gamma-ray emission site is around the Active Region on the solar surface. This implies that high-energy protons are produced at the Active region and that turbulent acceleration would be the most plausible option.Fermi data analysis for Active Galactic Nuclei (AGN) were also performed. In particular, 2 very-high-energy gamma-ray photons were detected from the close vicinity of the z=1.1 blazar PKS 0426-380.