  Solar Energetic Particles (SEPs) are an important component of Space Weather,
including radiation hazard to humans and electronic equipment, and the
ionisation of the Earth's atmosphere. We review the key observations of SEPs,
our current understanding of their acceleration and transport, and discuss how
this knowledge is incorporated within Space Weather forecasting tools.
Mechanisms for acceleration during solar flares and at shocks driven by Coronal
Mass Ejections are discussed, as well as the timing relationships between
signatures of solar eruptive events and the detection of SEPs in interplanetary
space. Evidence on how the parameters of SEP events are related to those of the
parent solar activity is reviewed and transport effects influencing SEP
propagation to near-Earth locations are examined. Finally, the approaches to
forecasting Space Weather SEP effects are discussed. We conclude that both
flare and CME shock acceleration contribute to Space Weather relevant SEP
populations and need to be considered within forecasting tools.
