Flux and Energy Spectrum of Cosmic-RayαParticles during Solar Maximum

Abstract

The fluxes of primary cosmic-ray $\alpha$ particles over Minnesota and Texas have been measured during the present period of maximum solar activity. A value of 136±9 $\alpha$ particles/${\mathrm{m}}^2$ sec sterad was measured over Minnesota and of 68±4 $\alpha$ particles/${\mathrm{m}}^2$ sec sterad over Texas. In both cases these values are significantly lower than those observed at solar minimum. The energy spectrum of these particles has been determined between 200 Mev/nucleon and 3.0 Bev/nucleon. It is shown that the slope of the integral spectrum is less than that observed at solar minimum and that a significant number of low-energy particles is still present. A possible mechanism for these changes is discussed briefly. The determination of energies of particles from a measurement of their ionization is discussed in detail in an appendix.