On the point-source approximation of nearby cosmic ray sources

Satyendra Thoudam, Jörg R. Hörandel

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


In this paper, we check in detail the validity of the widely adopted point-source approximation for nearby cosmic ray (CR) sources. Under an energy-independent escape model for CRs from the sources, we show that for young nearby sources, the point-source approximation breaks down at lower energies and the CR spectrum depends on the size and the morphology of the source. When applied to the nearby supernova remnants (SNRs), we find that the approximation breaks down for some of the individual remnants like the Vela, but interestingly it still holds good for their combined total spectrum at the Earth. Moreover, we also find that the results obtained under this simple approximation are quite different from those calculated under an energy-dependent escape model which is favoured by diffusive shock acceleration models inside SNRs. Our study suggests that if SNRs are the main sources of CRs in our Galaxy, then the commonly adopted point-source model (with an energy-independent escape scenario) appears flawed for CR studies from the nearby SNRs.

Original languageBritish English
Pages (from-to)624-637
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Jan 2012


  • Cosmic rays
  • ISM: supernova remnants


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