Particle acceleration mechanisms
High-energy particle acceleration is observed to proceed in a diverse variety of astrophysical sites ranging from the terrestrial aurorae to the most distant quasars. Particle acceleration is a fairly common channel for the release of large-scale kinetic, rotational, and magnetic energy. Physical mechanisms include electrostatic acceleration, stochastic processes, and diffusive shock energization. Cosmic-ray energy spectra have shapes which reflect escape, collisional, and radiative losses. The overall acceleration efficiency is controlled by the low-energy particle injection which may, in turn, feed back into the energization. Recent observational developments, which illustrate these general principles and raise fresh questions, are briefly summarized.
© 1994 The American Astronomical Society. Received 1993 March 16; accepted 1993 June 9. I am grateful to Jon Arons, F. Coroniti, and Hal Zirin for last minute advice and especially to Ian Axford for removing several misconceptions and infelicities from the manuscript. Support under NSF grant AST 89-17765 and NASA grant NAGW 2816 is gratefully acknowledged.
Published - particle_acceleration_mechanisms.pdf