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 GeV (the fastest particles can reach 80% of the speed of light). 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…