HR: 16:00h
AN: SM44A-01 INVITED     [Abstracts]
TI: The Acceleration of Fast Charged Particles in Space Plasmas
AU: * Jokipii, J R
EM: jokipii@lpl.arizona.edu
AF: University of Arizona, Dept of Planetary Sciences, Tucson, AZ 85721 United States
AB: Energetic particles, some with very high energies, are observed in space whereever the ambient matter density is low enough. In most cases the observed energy spectra of the particles are inverse power laws, with indices which range over a fairly narrow range. This suggests that the same mechanism may be accelerating most of the energetic particles. Acceleration of charged particles by collisionless shock waves has the desired attributes. Strong shock waves produce power-law energy spectra with indices which are quite insensitive to the detailed parameters of the specific situation, and the indices are close to those observed. All that is required is that the scattering by the turbulent magnetic field is sufficient that the the distribution functions are not too anisotropic in pitch angle and that the energetic-particle speeds are significantly larger than the ambient flow speed of the background plasma. I will discuss the physics of shock acceleration and demonstrate that it is the likely accelerator of most observed energetic particles. I will also show that there are situations where shock accelertion doesn't seem to be the answer, and briefly discuss alternative accelerators.
DE: 7514 Energetic particles (2114)
DE: 7807 Charged particle motion and acceleration
DE: 7851 Shock waves
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting