Cosmic-ray hydrodynamics at relativistic shocks

Journal Article · Mon Aug 01 04:00:00 EDT 1988 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/166559· OSTI ID:6726033

Kirk, J G; Webb, G M

A test particle description of first-order Fermi acceleration of cosmic rays at plane-parallel relativistic shocks is presented in which the pitch angle distribution is obtained explicitly and used to determine the pressure anisotropy or variable Eddington factor as a function of position. The Eddington factor is in turn used to find the hydrodynamical cosmic-ray sound speed, taking the anisotropy into account. For upstream flows speeds above c/sq rt 3, it is shown that the cosmic-ray sound speed exceeds the shock speed in a region just upstream of the shock and decreases montonically with distance further upstream, reaching the value c/sq rt 3 far from the shock. Thus, the shock succeeds in maintaining an anisotropy in the cosmic-ray distribution which is sufficient to keep the flow subsonic with respect to the cosmic-ray sound speed both downstream and in a finite region upstream. The astrophysical implications of these findings are discussed. 16 references.

• Research Organization: Max-Planck-Institut fuer Physik und Astrophysik, Garching (Germany, F.R.); Arizona Univ., Tucson (USA)
• OSTI ID: 6726033
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 331; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640101* -- Astrophysics & Cosmology-- Cosmic Radiation
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
ANISOTROPY
COSMIC RADIATION
EDDINGTON THEORY
ENERGY RANGE
FLUID MECHANICS
HYDRODYNAMICS
IONIZING RADIATIONS
MECHANICS
RADIATIONS
RELATIVISTIC RANGE
SHOCK WAVES
WAVE PROPAGATION