EDP Sciences
Free access
Volume 386, Number 3, May II 2002
Page(s) 829 - 832
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20020308

A&A 386, 829-832 (2002)
DOI: 10.1051/0004-6361:20020308

Cosmic ray acceleration at supergalactic accretion shocks: A new upper energy limit due to a finite shock extension

M. Ostrowski and G. Siemieniec-Ozieblo

Obserwatorium Astronomiczne, Uniwersytet Jagiellonski, ul. Orla 171, 30-244 Kraków, Poland

(Received 23 October 2001 / Accepted 18 February 2002)

Accretion flows onto supergalactic-scale structures are accompanied with large spatial scale shock waves. These shocks were postulated as possible sources of ultra-high energy cosmic rays. The highest particle energies were expected for perpendicular shock configuration in the so-called "Jokipii diffusion limit", involving weakly turbulent conditions in the large-scale magnetic field imbedded in the accreting plasma. For such configuration we discuss the process limiting the highest energy that particles can obtain in the first-order Fermi acceleration process due to finite shock extensions to the sides, along and across the mean magnetic field. Cosmic ray outflow along the shock structure can substantially lower the upper energy limit for conditions considered for supergalactic shocks.

Key words: ISM: cosmic rays -- acceleration of particles -- shock waves -- galaxies: clusters: general

Offprint request: G. Siemieniec-Ozieblo, grazyna@oa.uj.edu.pl

© ESO 2002