Evidence for the Dominence of Heavy Nuclei in Cosmic Rays at 10(5) GEV

Data from a recent experiment on the distribution of arrival time of energetic hadrons relative to associated air showers at mountain altitudes is reanalyzed. Monte Carlo simulations of air showers are used to derive the possible variations of abundance of heavy nuclei at high energies. Results show that the fraction of heavy nuclei increases at air-shower energies of about 100,000 GeV; this higher abundance is explained by various models of cosmic ray generation and transport. The analysis supports the theory that the heavy primaries are accelerated to spectra, which become progressively flatter with increasing charge, and that there is a differentiation between different nuclei due to a leakage from the galaxy at rigidities greater than 100,000 GV/c, when their gyroradii become comparable to the sizes of magnetic inhomogeneities in the interstellar medium. The observations also rule out models which postulate an increasingly rapid loss of particles from Galaxy rigidities as low as 10 GV/c.