TY - JOUR
T1 - Cosmic-ray time scales using radioactive clocks
AU - Yanasak, Nathan Eugene
AU - Wiedenbeck, M. E.
AU - Binns, W. R.
AU - Christian, E. R.
AU - Cummings, A. C.
AU - Davis, A. J.
AU - George, J. S.
AU - Hink, P. L.
AU - Israel, M. H.
AU - Leske, R. A.
AU - Lijowski, M.
AU - Mewaldt, R. A.
AU - Stone, E. C.
AU - Von Rosenvinge, T. T.
N1 - Funding Information:
ACKNOWLEDGMENTS This work was supported by NASA (under NAG5-6912) at the California Institute of Technology, the Jet Propulsion Laboratory, Washington University, and Goddard Space Flight Center.
PY - 2001
Y1 - 2001
N2 - 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.
AB - 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.
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U2 - 10.1016/S0273-1177(01)00114-4
DO - 10.1016/S0273-1177(01)00114-4
M3 - Article
AN - SCOPUS:6644227746
SN - 0273-1177
VL - 27
SP - 727
EP - 736
JO - Advances in Space Research
JF - Advances in Space Research
IS - 4
ER -