Acceleration of cosmic rays by shock waves
Shafer Institute of Cosmophysical Research and Aeronomy, Siberian Branch of the RAS, 31 Lenin Ave., Yakutsk, 677980, Russian Federation
Theoretical work on various processes by which shock waves accelerate cosmic rays is reviewed.
The most efficient of these processes, Fermi acceleration, is singled out for special attention. A
linear theory for this process is presented. The results found on the basis of nonlinear models of
Fermi acceleration, which incorporate the modification of the structure caused by the accelerated
particles, are reported. There is a discussion of various possibilities for explaining the generation
of high-energy particles observed in interplanetary and interstellar space on the basis of a Fermi
acceleration mechanism. The acceleration by shock waves from supernova explosions is
discussed as a possible source of galactic cosmic rays. The most important unresolved questions in
the theory of acceleration of charged particles by shock waves are pointed out.