Composition of cosmic radiation at energies approx. 10/sup 15/ eV and above

Experimental data on relative fluctuations of the fluxes of electrons and muons in extensive air showers have been used to determine the nuclear composition of the primary cosmic radiation in the energy range 10/sup 15/--10/sup 17/ eV. The analysis of the experimental data does not involve assumptions regarding hadron-multiple-production processes at ultrahigh energies, since any models which are consistent with the averaged dependence of the number of muons in an extensive shower on the number of electrons, which has been thoroughly investigated in many experiments, are acceptable for this purpose. On the basis of the present work and previously published results of other authors on the intensity of the fluxes of protons and various nuclei at the edge of the atmosphere, and also on the basis of data on the total flux of primary particles in the energy range 10/sup 14/--10/sup 18/ eV, we have obtained approximations of the energy spectra of primary protons and heavier nuclei in the energy interval 10/sup 12/--10/sup 18/ eV. Over this entire range the composition of the primary cosmic radiation with respect to the relative contribution of protons and various nuclei remains approximately constant.