Solar energetic particles

Solar energetic particles (SEP) are high-energy particles coming from the Sun. They were first observed in the early 1940s. 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 (SEP) are high-energy particles coming from the Sun. They were first observed in the early 1940s. 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). However, only about 1% of CMEs produce strong SEP events.