The Cosmic-Ray Intensity Above the Atmosphere at the Geomagnetic Equator

By means of G-M counter telescopes in an Aerobee sounding rocket fired from the USS Norton Sound, total charged particle cosmic-ray intensity above the atmosphere has been measured at the geomagnetic equator. An empirical zenith angle ($\theta$) dependence of directional intensity, averaged over all azimuths, is found to be $j\left(\theta \right)=0.028(1+0.6\mathrm{}sin\theta )$, in which $j\left(\theta \right)$ is in absolute units ${(\mathrm{s}\mathrm{e}\mathrm{c}.{\mathrm{cm}}^2\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{n})}^{-1\mathrm{}}$. The deduced vertical intensity 0.028/sec./${\mathrm{cm}}^2$/steradian is thought to be most nearly free of atmospheric albedo and, therefore, to be our best estimate of an upper limit for the primary intensity of charged particles of energy greater than 14 Bev (for protons). A comparison is made with previous results at geomagnetic latitude 41°N.