Effect of losses on acceleration of energetic particles by diffusive scattering through shock waves

Journal Article · Thu Oct 01 00:00:00 EDT 1981 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/159272· OSTI ID:5542401

Voelk, H J; Morfill, G E; Forman, M A

The effect of local losses on the acceleration of energetic particles by shocks is discussed considering both energy losses of individual particles and damping processes for the scattering hydromagnetic waves. The calculations are all time asymptotic and steady state. For locally plane and infinitely extended shocks, the requirement for acceleration is that the loss time exceed the acceleration time. The resulting modifications of the spatial structure and of the momentum dependence of the cosmic-ray distribution are described. For acceleration to be a local effect within the Galaxy, the local scattering mean free path must be small compared to the effective overall galactic mean free path as deduced from the cosmic-ray escape time. The required strengths of the scattering wave fields are such that neutral molecular clouds do not allow acceleration; in a partially ionized, warm interstellar medium, quite large shock strengths are needed. Such strong shock discontinuities are surrounded by an ionization layer within which Alfven wave damping is presumably negligible. Given the spatial extent of the layer for strong shocks propagating into neutral interstellar clouds, the possibility of localized diffusive acceleration is investigated. The estimated strength and extent of the scattering region is not large enough to confine acceleration within the layer. Rather, it will extend across the whole cloud, whose integrated losses then determine the efficiency.

• Research Organization: Max-Planck-Institut fuer Kernphysik
• OSTI ID: 5542401
• Journal Information: Astrophys. J.; (United States), Vol. 249:1
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
INTERSTELLAR SPACE
SHOCK WAVES
PLASMA
PLASMA ACCELERATION
ALFVEN WAVES
COSMIC RADIATION
COSMIC RAY PROPAGATION
DIFFUSION
IONIZATION
MEAN FREE PATH
MILKY WAY
STEADY-STATE CONDITIONS
WAVE PROPAGATION
ACCELERATION
GALAXIES
HYDROMAGNETIC WAVES
IONIZING RADIATIONS
RADIATIONS
SPACE
640105* - Astrophysics & Cosmology- Galaxies