Fermi Acceleration of Charged Particles.
Abstract
Two efficient types of Fermi acceleration by hydromagnetic shocks are presented. One is based on Parker's (1958a) work on acceleration between shocks which cross each other. An equivalent situation is that of a single shock crossing a closed magnetic line of force. It is shown that a net gain in particle energy occurs even if the shocks are weak A second type is the acceleration by a shock which moves into stronger magnetic fields. While the particle is accelerated ahead of the shock and is able to penetrate stronger fields, the shock field may become sufficiently stronger that the particle is unable to escape the trap and is accelerated for a long time No such prolonged trapping occurs for the same particle decelerated behind a similar shock moving into weaker fields, so that the net efficiency of acceleration is high. Conditions on acceleration of thermal particles, specifically electrons, are discussed. One condition is that the particle must move faster than the shock.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 1963
- DOI:
- 10.1086/147490
- Bibcode:
- 1963ApJ...137..135W