Cosmic-ray time scales using radioactive clocks

Nathan Eugene Yanasak, M. E. Wiedenbeck, W. R. Binns, E. R. Christian, A. C. Cummings, A. J. Davis, J. S. George, P. L. Hink, M. H. Israel, R. A. Leske, M. Lijowski, R. A. Mewaldt, E. C. Stone, T. T. Von Rosenvinge

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Radionuclides in the galactic cosmic rays serve as chronometers for measuring the characteristic time of physical processes affecting cosmic ray energy spectra and composition. The radionuclide 59 Ni, present in the ejecta of supernovae, will decay to 59 Co via electron-capture with a halflife of T 1/2 = 7.6 × 10 4 yr. However, if the cosmic ray acceleration time scale is shorter than the decay halflife, 59 Ni will become fully-stripped of electrons and will be present in the cosmic rays. Abundances of cosmic ray 59 Ni and 59 Co measured with the Cosmic Ray Isotope Spectrometer (CRIS) are consistent with the decay of all source 59 Ni, implying an acceleration time delay > 10 5 yr. Abundances of the βs-decay radioactive secondaries, produced by fragmentation of the cosmic rays during transport in the interstellar medium (ISM), depend on the time scales for spallation and escape from the Galaxy. Consequently, measurement of these abundances can be used to derive the galactic confinement time, T esc , for cosmic rays. Using the abundances of the βs-decay species 10 Be, 26 Al, 36 Cl, and 54 Mn measured by CRIS, we find a confinement time T esc ~ 15 Myr. Published by Elsevier Science Ltd on behalf of COSPAR.

Original languageEnglish (US)
Pages (from-to)727-736
Number of pages10
JournalAdvances in Space Research
Issue number4
StatePublished - 2001

ASJC Scopus subject areas

  • Aerospace Engineering
  • Astronomy and Astrophysics
  • Geophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences(all)


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