The abundances and energy spectra of cosmic ray iron and nickel at energies from 1 to 10 GeV per amu

A scintillation-Cerenkov counter telescope has been used to measure the absolute flux and energy spectra of the nuclear components of the primary cosmic radiation. This instrument has been flown twice on high-altitude balloons launched from Muskogee, Okalahoma (vertical rigidity cutoff of 3.4 GV), and has provided a total exposure of 20 sq m sr hr. In this paper the measurements of the abundances and the differential energy spectra of iron and nickel in the energy interval from 1 to 10 GeV per amu are presented. The mean abundance of nickel relative to iron is found to be 0.050 + or - 0.003. This ratio is consistent with abundances at the source which are similar to those of the interstellar medium as estimated both by Meyer (1979) and by Cameron (1970). If the measured energy spectra are fit to single power laws in total energy, spectral indices of 2.44 + or - 0.07 for iron and 2.33 + or - 0.13 for nickel are obtained.