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[11.07] Measurement of the Cosmic Ray \beta-decay Secondary Abundances and Implications for Cosmic Ray Propagation

N.E. Yanasak, M.E. Wiedenbeck (JPL), A.C. Cummings, J.S. George, R.A. Leske, R.A. Mewaldt, E.C. Stone (CIT), E.R Christian, T.T. von Rosenvinge (NASA/GSFC), W.R. Binns, P.L. Hink, J. Klarmann, M. Lijowski (Wash. U.)

We report on isotopic abundance measurements of the \beta-decay galactic cosmic ray (GCR) secondaries observed by the Cosmic Ray Isotope Spectrometer(CRIS) aboard the Advanced Composition Explorer spacecraft. Propagation of the GCRs produces secondary fragments as they spall during passage through the interstellar medium (ISM). The abundances of these secondaries depends on the amount of ISM material traversed by the GCRs and the mean free path for leakage out of the galaxy. The production and subsequent decay during propagation of radioactive secondaries allows long-lived species to act as probes of the local density of the ISM and propagation duration. ¹⁰Be, ²⁶Al, ³⁶Cl, and ⁵⁴Mn are suitable for this study, providing a comparison of propagation histories for different parent nuclei and sampling over different volumes of the ISM, owing to their different halflives. To interpret the data we have modeled the production and propagation of the radioactive secondaries, using recently published isotopic production cross-sections. We discuss the results of these calculations and their implications for GCR transport and the local ISM. Supported by NASA at Caltech (grant NAG5-6912), JPL, GSFC, and Wash. U.

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