Published in Space Science Reviews, Volume 134, Issue 1-4, pp. 119-140, 2008.
astro-ph/0801.0995

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COSMOLOGICAL SHOCK WAVES

A.M. Bykov 1, K. Dolag 2 and F. Durret 3


1 A.F. Ioffe Institute of Physics and Technology, St. Petersburg, 194021, Russia
byk@astro.ioffe.ru
2 Max Planck Institut für Astrophysik, P.O. Box 1317, D-85741 Garching, Germany
kdolag@mpa-garching.mpg.de
3 Institut d'Astrophysique de Paris, CNRS, Université Pierre et Marie Curie, 98bis Bd Arago, F-75014 Paris, France
durret@iap.fr


Abstract. Large-scale structure formation, accretion and merging processes, AGN activity produce cosmological gas shocks. The shocks convert a fraction of the energy of gravitationally accelerated flows to internal energy of the gas. Being the main gas-heating agent, cosmological shocks could amplify magnetic fields and accelerate energetic particles via the multi-fluid plasma relaxation processes. We first discuss the basic properties of standard single-fluid shocks. Cosmological plasma shocks are expected to be collisionless. We then review the plasma processes responsible for the microscopic structure of collisionless shocks. A tiny fraction of the particles crossing the shock is injected into the non-thermal energetic component that could get a substantial part of the ram pressure power dissipated at the shock. The energetic particles penetrate deep into the shock upstream producing an extended shock precursor. Scaling relations for postshock ion temperature and entropy as functions of shock velocity in strong collisionless multi-fluid shocks are discussed. We show that the multi-fluid nature of collisionless shocks results in excessive gas compression, energetic particle acceleration, precursor gas heating, magnetic field amplification and non-thermal emission. Multi-fluid shocks provide a reduced gas entropy production and could also modify the observable thermodynamic scaling relations for clusters of galaxies.


Key words: large scale structure of universe - shock waves - acceleration of particles - X-rays: galaxies: clusters


Table of Contents

INTRODUCTION

SINGLE-FLUID MHD-SHOCKS

COLLISIONLESS SHOCKS
Micro processes in collisionless shocks
Heating of ions in collisionless shocks
Heating of electrons in collisionless shocks
Gas heating and entropy production in weak internal shocks

ENERGETIC PARTICLE ACCELERATION IN COLLISIONLESS SHOCKS

COSMIC-RAY MODIFIED MULTIFLUID SHOCKS
Magnetic field amplification in CR-dominated shocks
Gas heating and entropy production in strong CR-modified shocks
ICM entropy production by multifluid accretion shocks

SHOCKS IN LARGE-SCALE STRUCTURE
Evidence for shocks in galaxy clusters

SUMMARY

REFERENCES

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