The Altitude and Latitude Variation in the Rate of Occurrence of Nuclear Disintegrations Produced in the Stratosphere by Cosmic Rays

The variation with altitude of the rate of production of stars in photographic plates was measured from mountain elevations to 94,000 feet at geomagnetic latitude $\lambda \simeq 54$°N. The type of particle initiating each star was determined and showed that the total flux of star-producing protons decreased rapidly from 94,000 feet to 11,500 feet and was compatible with an absorption mean free path (m.f.p.) of 145 g/${\mathrm{cm}}^2$. The total flux of star-producing neutrons showed a maximum near 70,000 feet and then decreased with altitude with an absorption mean free path of 170 g/${\mathrm{cm}}^2$. Similar altitude dependence measurements were made at $\lambda \simeq 28$°N and showed that the rate of production by neutrons of stars of 3 to 9 prongs at 94,000 feet was 0.19 of the corresponding value at $\lambda \simeq 54°$. This demonstrates that 81 percent of the small stars at $\lambda \simeq 54°$ must be due to the primary particles of the cosmic radiation in the energy intervals given by the geomagnetic cut-off at $\lambda \simeq 28°$ and $\lambda \simeq 54°$ (1 to 8 Bev for protons, and for $\alpha$-particles and heavy nuclei 0.35 to 3.5 Bev per nucleon). The total flux of star-producing protons varies by a factor of 3.0 between these two latitudes at 94,000 feet and shows that 67 percent of the proton-initiated stars at $\lambda \simeq 54$ are due to primary particles of the energies given above.