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Published 1973 | Published
Book Section - Chapter Open

Measurement of the Cosmic-Ray Be/B Ratio and the Age of Cosmic Rays


The ratio Be/B depends on whether the confinement time of cosmic rays in the Galaxy is long or short compared to the radioactive half-life of ^(10)Be. We report observations of this ratio which were obtained with a dE/dx-Cerenkov detector launched into a polar orbit on OGO-6 as part of the Caltech Solar and Galactic Cosmic Ray Experiment. Be/B ratios were determined for various rigidity thresholds up to 15 GV. We find no statistically significant rigidity dependence of the ratio, which is 0.41 ± 0.02 when averaged over all observed cutoffs. When averaged over cutoffs ≥1.8 GV, the ratio is 0.43 ± 0.03, which can be compared directly to the ratio of 0.42 ± 0.06 calculated by O'Dell, Shapiro, Silberberg, and Tsao assuming ^(10)Be survival. Additional calculations suggest that if the present fragmentation parameters are correct, then the lifetime of cosmic rays in the Galaxy is < 10^7 y.

Additional Information

© 1973 University of Colorado. Provided by the NASA Astrophysics Data System. Dr. S. S. Murray made significant contributions to the OGO-6 program. Dr. J. Audouze kindly provided us with a copy of the computer program for the propagation calculation and provided us with cross section data. Dr. M. Shea kindly supplied us with detailed geomagnetic cutoff data, and Dr. T. L. Garrard supplied the solar modulation program. We appreciate discussions with Dr. C. Cesarsky. One of us (Brown) received support from the National Science Foundation, while another (Stone) was an Alfred P. Sloan research fellow. This work was supported in part by NASA contract NAS5-9312 and grant NGR 05-002-160.

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August 19, 2023
October 26, 2023