Quantitative estimates of the effects of cross section uncertainties on the derivation of GCR source composition

Cosmic-ray source abundance uncertainties, resulting from the cross-section uncertainties, are calculated for the elements carbon through nickel. A significant dominance of cross-section errors in the source abundance uncertainties is found for most of the elements considered, even with uncorrelated partial cross-section errors; much larger uncertainties than those reported previously are found for Ca, N, Na, Al, and S. Propagation errors are noted to preclude a significant determination of source abundances for F, Cl, and Mn. A need for an assessment of the existing cosmic-ray propagation models - especially the propagation cross-sections which they employ - is expressed, motivated by recent improvements in the resolution and statistical accuracy of observations.