Cosmic ray production in supernova remnants including reacceleration: The secondary to primary ratio

Free access article

Issue		A&A Volume 410, Number 1, October IV 2003


Page(s)		189 - 198
Section		Formation, structure and evolution of stars
DOI		http://dx.doi.org/10.1051/0004-6361:20031274

A&A 410, 189-198 (2003)
DOI: 10.1051/0004-6361:20031274

Cosmic ray production in supernova remnants including reacceleration: The secondary to primary ratio

E. G. Berezhko¹, L. T. Ksenofontov^{1, 2}, V. S. Ptuskin³, V. N. Zirakashvili³ and H. J. Völk⁴

¹ Institute of Cosmophysical Research and Aeronomy, 31 Lenin Ave., 677891 Yakutsk, Russia
    e-mail: berezhko@ikfia.ysn.ru
² Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582, Japan
    e-mail: ksenofon@icrr.u-tokyo.ac.jp
³ Institute for Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Troitsk, Moscow region 142092, Russia
    e-mail: vptuskin@izmiran.rssi.ru; zirak@izmiran.rssi.ru
⁴ Max-Planck-Institut für Kernphysik, Postfach 103980, 69029 Heidelberg, Germany

(Received 16 April 2003 / Accepted 29 July 2003 )

Abstract
We study the production of cosmic rays (CRs) in supernova remnants (SNRs), including the reacceleration of background galactic cosmic rays (GCRs) - thus refining the early considerations by Blandford & Ostriker (1980) and Wandel et al. (1987) - and the effects of the nuclear spallation inside the sources (the SNRs). This combines for the first time nuclear spallation inside CR sources and in the diffuse interstellar medium, as well as reacceleration, with the injection and subsequent acceleration of suprathermal particles from the postshock thermal pool. Selfconsistent CR spectra are calculated on the basis of the nonlinear kinetic model. It is shown that GCR reacceleration and CR spallation produce a measurable effect at high energies, especially in the secondary to primary (s/p) ratio, making its energy-dependence substantially flatter than predicted by the standard model. Quantitatively, the effect depends strongly upon the density of the surrounding circumstellar matter. GCR reacceleration dominates secondary CR production for a low circumstellar density. It increases the expected s/p ratio substantially and flattens its spectrum to an almost energy-independent form for energies larger than 100 GeV/n if the supernovae explode on average into a hot dilute medium with hydrogen number density $N_{\rm H}=0.003$ cm ^-3. The contribution of CR spallation inside SNRs to the s/p ratio increases with increasing circumstellar density and becomes dominant for $N_{\rm H}\ga 1$ cm ^-3, leading at high energies to a flat s/p ratio which is only by a factor of three lower than in the case of the hot medium. Measurements of the boron to carbon ratio at energies above 100 GeV/n could be used in comparison with the values predicted here as a consistency test for the supernova origin of the GCRs.

Key words: ISM: cosmic rays -- shock waves -- stars: supernovae: general

Offprint request: H. J. Völk, heinrich.voelk@mpi-hd.mpg.de

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