Astron. Astrophys. 330, 389-398 (1998)

1. Introduction

The origin of cosmic rays (Hess 1912, Kohlhörster 1913) is still one of the main enigmas of physics. Many energetic sources have been claimed to explain parts of the population of cosmic ray particles observed. Novae, pulsars, supernova explosions, stellar wind bubbles, interstellar turbulence, radio galaxies and many other sources have been explored (Fermi 1949, 1954; Peters 1959, 1961; Berezinsky et al. 1990).

1.1. The origin of cosmic rays

Recently we have proposed that cosmic rays can be traced to three different source sites:

• 1. Supernova explosions into the interstellar medium, or ISM-SNe. This component produces mostly hydrogen and the observed energetic electrons up to about 30 GeV, and dominates the all particle flux up to near GeV.
• 2. Supernova explosions into the predecessor stellar wind, wind-SNe. This component produces the observed energetic electrons above 30 GeV, and helium and most heavier elements already from GeV particle energies. Due to a reduction in acceleration efficiency at a particular rigidity the slope increases, thus producing the knee feature. The component extends ultimately to several EeV. Since the winds of massive stars are enriched late in their life, this component shows a heavy element abundance which is strongly increased over the interstellar medium.
• 3. Powerful radio galaxies produce a contribution which dominates beyond about 3 EeV, and consists mostly of hydrogen and helium, with only little addition of heavy elements below 50 EeV. At this energy the interaction with the microwave background cuts off the contribution from distant extragalactic sources, the Greisen-Zatsepin-Kuzmin (GZK) cutoff. There are a small number of events which appear to be beyond this energy, and whether they fit into such a picture is open at present.

The theory was originally proposed in Biermann (1993a, paper CR I) and in Rachen & Biermann (1993, paper UHE CR I). Various tests were performed in Biermann & Cassinelli (1993, paper CR II); Biermann & Strom (1993, paper CR III); Stanev et al. (1993, paper CR IV); Rachen & Biermann (1993, paper UHE CR I); Rachen et al. (1993, paper UHE CR II); Nath & Biermann (1993, 1994a, 1994b); Biermann et al. (1995a); Biermann et al. (1995b, paper CR V); Stanev et al. (1995); Biermann et al. (1997) and Biermann (1993b, c, 1994, 1995a, b, 1996, 1997a, 1997b).

In this paper we will at first briefly discuss the error determination of the theory in Sect. 2, then the data for individual elements in Sect. 3, compare and discuss secondary elements versus primary elements in Sect. 4, and conclude in Sect. 5.

© European Southern Observatory (ESO) 1998

Online publication: January 8, 1998
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