Primary and secondary contributions to arriving abundances of cosmic-ray nuclides

Abstract

The arriving abundances of a variety of cosmic-ray nuclides consist of comparable amounts of primary material produced by stellar nucleosynthesis and secondary matter resulting from fragmentation of heavier nuclei by collisions during interstellar propagation. In order to utilize such species in studies of cosmic-ray source composition it is necessary to determine the secondary fraction present in the arriving material and to assess the uncertainty in this determination. We have extracted the primary and secondary contributions to the arriving abundances for isotopes of elements between B and Ni by using 1) measurements of cosmic-ray elemental and isotopic composition obtained from the Cosmic Ray Isotope Spectrometer (CRIS) instrument on the Advanced Composition Explorer (ACE) spacecraft, 2) a data base of measured and calculated fragmentation cross sections, and 3) a leaky box model of interstellar propagation. We present derived decompositions and discuss their implications for studies of the composition of cosmic-ray source material. This work was supported by NASA at Caltech (under grant NAG5-12929), JPL, Washington University, and GSFC.

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