Particle Acceleration by Waves and Fields

Abstract

The acceleration of electrons and charged nuclei to high energies is a phenomenon occuring at many sites throughout the universe, including the galaxy, pulsars, quasars, and around black holes. In the heliosphere, large solar flares and the often associated coronal mass ejections (CMEs) are the most energetic natural particle accelerators, occasionally accelerating protons to GeV and electrons to tens of MeV energies. The observation of these particles offers the unique opportunity to study fundamental processes in astrophysics. Particles that escape into interplanetary space can be observed in situ with particle detectors on spacecraft. In particular, particle spectra can be diagnostic of flare acceleration processes. On the other hand, energetic processes on the sun can be studied indirectly, via observations of the electromagnetic emissions (radio, X-ray, gamma-ray) produced by the particles in their interactions with the solar atmosphere. The purpose of this article is to give a brief overview on current models on particle acceleration and the present status of observations of solar energetic particles.