Origin of Galactic Cosmic Rays

By P. Blasi. 2012

135 citations recorded by the source corpus.

Abstract The origin of the bulk of cosmic rays (CRs) observed at Earth is the topic of a century long investigation, paved with successes and failures. From the energetic point of view, supernova remnants (SNRs) remain the most plausible sources of CRs up to rigidity ∼ 10 6 – 10 7 GV . This confidence somehow resulted in the construction of a paradigm, the so-called SNR paradigm: CRs are accelerated through diffusive shock acceleration in SNRs and propagate diffusively in the Galaxy in an energy dependent way. Qualitative confirmation of the SNR acceleration scenario has recently been provided by gamma ray and X-ray observations. Diffusive propagation in the Galaxy is probed observationally through measurement of the secondary to primary nuclei flux ratios (such as B/C). There are however some weak points in the paradigm, which suggest that we are probably missing some physical ingredients in our models. The theory of diffusive shock acceleration at SNR shocks predicts spectra of accelerated particles which are systematically too hard compared with the ones inferred from gamma ray observations. Moreover, hard injection spectra indirectly imply a steep energy dependence of the diffusion coefficient in the Galaxy, which in turn leads to anisotropy larger than the observed one. Moreover recent measurements of the flux of nuclei suggest that the spectra have a break at rigidity ∼ 200 GV , which does not sit well with the common wisdom in acceleration and propagation. In this paper I will review these new developments and suggest some possible implications.

Subfields: Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/1eda008d1d4ba360719f1ecee9dce07569be3211

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In Nuclear and High Energy Physics

Citations in the corpus

Massive stars as major factories of Galactic cosmic rays (2018, methodology): “stributionsoftheobservedγ-rayimagesofobjectsdiscussedinthispaper do not agree with this prediction. It is convenient to write the radial distribution of the CR density in the form w(r) = w0(r/r0)−1 . (2) Below we will adopt r0 = 10 pc, i.e. normalise the CR proton density w0 outside but not far from”
The Nine Lives of Cosmic Rays in Galaxies (2015, background): “…of the 1912 discovery of cosmic rays has passed, accompanied by commemorative celebrations (Ormes 2013) and reviews (Blandford, Simeon & Yuan 2014; Blasi 2013; Kotera & Olinto 2011; Slane et al. 2014; Zweibel 2013), which highlighted the impressive historical progress on the continuing questions…”