Current views on impulsive and gradual solar energetic particle events

Abstract

Solar energetic particles (SEPs) are one manifestation of violent energy releases on: the Sun. The study of their acceleration and propagation reveals information about basic plasma-physical processes, such as reconnection, shock acceleration and wave-particle interaction, in astrophysical objects, such as stars, magnetospheres or the diluted plasma of the interstellar or interplanetary medium. This paper introduces the current classification scheme for solar energetic particle events, its relation to the underlying acceleration processes, and addresses open questions regarding the better understanding of SEPs as well as the underlying physical processes: Modifications to the current paradigm considering more recent observations will be suggested.