3.1.2.1 Understand energy release and particle acceleration process

Large solar flares rapidly accelerate ions up to many GeV and electrons up to 10s of MeV, and they could be a significant contributor to the SEPs observed in space in gradual events. Imaging in hard X-rays generated by accelerated electrons, and in the 2.223 MeV neutron-capture γ-ray line produced by accelerated >~30 MeV ions, show that these emissions come from the footpoints of newly formed loops (Hurford et al, 2006). Furthermore, the accelerated >~20 keV electrons and >~ few MeV ions often contain >~10-50% of the energy released in the flare (Lin & Hudson 1976; Lin et al 2003), suggesting that the particle acceleration is intimately related to the magnetic reconnection process that appears to release the flare energy. Neither the energy release or particle acceleration processes are understood, but some accelerated particles could end up on magnetic field lines connected to the heliosphere, as observed in many impulsive events.