{
  "id": "astro-ph/0111555",
  "version": "v1",
  "published": "2001-11-29T12:47:35.000Z",
  "updated": "2001-11-29T12:47:35.000Z",
  "title": "On the Origin of Cosmic Rays",
  "authors": [
    "R. Plaga"
  ],
  "comment": "27 pages, Latex, 5 eps figures",
  "categories": [
    "astro-ph"
  ],
  "abstract": "The problem in identifying the sites of origin of Galactic Cosmic Rays (CRs) is reviewed. Recent observational evidence from very-high energy (VHE, energies above 100 GeV) gamma-ray measurements is in contradiction with the surmise that synchrotron radiation from relativistic electrons is indicative for hadron acceleration. It rather points to a CR-acceleration efficiency of supernova remnants (SNRs) below one percent, much less than the value required if these objects were to be the main sources of Galactic cosmic rays (about 30%). Observations of CR anisotropy and the emission of low-energy (energy < 10 GeV) gamma-rays from the Galactic disk indicate that the sources of low-energy cosmic rays are distributed with a Galactocentric radial scale length in the order of 25 +- 10 kpc, much larger than expected if SNRs are the main sources of CRs. These two facts - together with the body of evidence from CR isotope abundances - strongly suggest that a new class of astrophysical objects - distinct from SNRs and located manly in the outer reaches of our Galaxy - is the major source of hadronic CRs in our Galaxy. The basic observational features of ultra high-energy (UHE, energy > 10^{19} eV) CRs are most naturally understood if the same CR sources accelerate CRs up to the highest observed CR energies. Proposals for the nature of a new source class are mentioned. The origin of CRs is still as much shrouded in mystery as it was in 1957, when Philip Morrison wrote a seminal review about CR origin. The potential for discoveries is thus great.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2001-11-29T12:47:35.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "galactic cosmic rays",
      "cr sources accelerate crs",
      "philip morrison wrote",
      "cr-acceleration efficiency",
      "supernova remnants"
    ],
    "note": {
      "typesetting": "LaTeX",
      "pages": 27,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 567461,
      "adsabs": "2001astro.ph.11555P"
    }
  }
}