PROPAGATION AND SOURCE ENERGY SPECTRA OF COSMIC RAY NUCLEI AT HIGH ENERGIES

A recent measurement of the TRACER instrument on long-duration balloon has determined the individual energy spectra of the major primary cosmic ray nuclei from oxygen (Z = 8) to iron (Z = 26). The measurements cover a large range of energies and extend to energies beyond 10(14) eV. We investigate if the data set can be described by a simple but plausible model for acceleration and propagation of cosmic rays. The model assumes a power-law energy spectrum at the source with a common spectral index a for all nuclear species, and an energy-dependent propagation path length (Lambda proportional to E-0.6) combined with an energy-independent residual path length Lambda(0). We find that the data can be fitted with a fairly soft source spectrum (alpha = 2.3-2.4), and with a residual path length Lambda(0) as high as 0.3 g cm(-2). We discuss this model in the context of other pertinent information, and we determine the relative abundances of the elements at the cosmic ray source.