Origin and Properties of Solar Energetic Particles in Space

Abstract

Transient energetic (E> 10 MeV) particle events from the Sun have been observed at the Earth for half a century using several detection techniques. We review these observations and the change in focus from solar flares to fast coronal mass ejections (CMEs) and shocks as the causal agents of solar energetic particle (SEP) events. We review the properties of SEP events that are important for space weather: 1) the number distributions of peak SEP intensities and of SEP fluences; 2) the relationship of SEP intensities to CME speeds; 3) when SEP events occur during the solar cycle; and 4) where SEP events occur relative to the CME-driven shocks. We conclude with a discussion of two cases of direct negative effects of SEPs on space experiments.