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 journalArticle

8 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 59Ni, present in the ejecta of supernovae, will decay to 59Co via electron-capture with a halflife of T1/2 = 7.6 × 104 yr. However, if the cosmic ray acceleration time scale is shorter than the decay halflife, 59Ni will become fully-stripped of electrons and will be present in the cosmic rays. Abundances of cosmic ray 59Ni and 59Co measured with the Cosmic Ray Isotope Spectrometer (CRIS) are consistent with the decay of all source 59Ni, implying an acceleration time delay > 105 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, Tesc, for cosmic rays. Using the abundances of the βs-decay species 10Be, 26Al, 36Cl, and 54Mn measured by CRIS, we find a confinement time Tesc ~ 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 - Aug 2 2001

ASJC Scopus subject areas

  • Aerospace Engineering
  • Space and Planetary Science

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    Yanasak, N. E., Wiedenbeck, M. E., Binns, W. R., Christian, E. R., Cummings, A. C., Davis, A. J., George, J. S., Hink, P. L., Israel, M. H., Leske, R. A., Lijowski, M., Mewaldt, R. A., Stone, E. C., & Von Rosenvinge, T. T. (2001). Cosmic-ray time scales using radioactive clocks. Advances in Space Research, 27(4), 727-736.