 They consist of protons, electrons and HZE ions with energy ranging from a few tens of keV to many GeV (the fastest particles can approach the speed of light, as in a "ground-level event").They are of particular interest and importance because they can endanger life in outer space (especially particles above 40 MeV).Solar energetic particles can originate either from a solar-flare site or by shock waves associated with coronal mass ejections (CMEs).