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Evidence against stellar chromospheric origin of Galactic cosmic rays

Nature volume 396, pages 50–52 (1998)Cite this article

Abstract

Interstellar space is filled with a gas of relativistic ions and electrons — the Galactic cosmic rays. These energetic particles tie interstellar gas to ambient magnetic fields by ionizing the component molecules and atoms, and so play a role in stabilizing molecular clouds against collapse1 and regulating the collapse of protostellar clouds2. The observed energy spectrum of cosmic rays up to ≳1015 eV is consistent with their acceleration by supernova shock waves3, but the original source of cosmic-ray nuclei remains unclear. There has been a widely held belief that the source consists of a solar-like ionized medium4, probably the chromospheres of late-type Sun-like stars5. This model predicts an overabundance of easily ionized elements. Here we show that lead, which is easily ionized, is underabundant in the Galactic cosmic rays in contradiction with this model. Rather, our measurements are consistent with two other possible models: one in which the nuclei originate in interstellar gas, and in entire grains accelerated to about one per cent of the speed of light by supernova shock waves6,7; and another in which the cosmic rays contain an admixture of an exotic, freshly synthesized component8, probably originating in neutrino-driven winds from newly born neutron stars9.

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Figure 1: Histogram of measured charges for GCR ions with kinetic energies >0.9 GeV per nucleon.
Figure 2: Derived GCR source abundances of Hg, Pb and actinides with respect to the Pt-group elements (75 ⩽ Z ⩽ 79).

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Acknowledgements

We thank D. O'Sullivan, M. Solarz, V. Akimov, Y. He, the staff at the AGS, and the crews of Mir and STS-74 for their assistance. We also thank the UHIC collaboration for providing measured cross-sections, and C. J. Waddington, B. S. Mayer and J.-P. Meyer for calculations and discussions.

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Author notes

  1. Vladimir G. Afanasiev

    Present address: Genesys Corporation, San Francisco, California, 94103, USA

Authors and Affiliations

  1. Department of Physics and Space Sciences Laboratory, University of California at Berkeley, Berkeley, 94720, California, USA

    Andrew J. Westphal, P. Buford Price, Benjamin A. Weaver & Vladimir G. Afanasiev

Authors
  1. Andrew J. Westphal
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  2. P. Buford Price
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  3. Benjamin A. Weaver
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  4. Vladimir G. Afanasiev
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Correspondence to Andrew J. Westphal.

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Westphal, A., Price, P., Weaver, B. et al. Evidence against stellar chromospheric origin of Galactic cosmic rays. Nature 396, 50–52 (1998). https://doi.org/10.1038/23887

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