Energetic particles in plasma astrophysics

Cosmic ray and gamma-ray astrophysics provides an arena where concepts draw n from many branches of plasma physics can assist in answering questions of fundamental-indeed cosmological-significance. In recent years, striking ad vances have been made in the quality and resolution of the data available i n this field. The present generation of cosmic ray detection arrays and spa ce-based x-ray and gamma-ray observatories, coupled to measurements in othe r wavebands, are yielding information which invites detailed quantitative i nterpretation in terms of plasma processes. In parallel with these developm ents, a systematic picture of the behaviour of energetic particle populatio ns in magnetically confined plasmas has emerged from the deuterium-tritium experimental campaigns on JET and TFTR, and the acceleration of electrons t o highly relativistic energies has been demonstrated in laser-plasma intera ction experiments. This review is written primarily to assist the deploymen t in energetic particle astrophysics of methodologies used for studying hig h-temperature fusion plasmas: three topics are examined. What are the major plasma-oriented questions in energetic particle astrophysics? What solutio ns have been proposed? How can plasma physics assist in deepening, strength ening and extending current understanding?