The Primary Specific Ionization and Intensity of the Cosmic Radiation above the Atmosphere at the Geomagnetic Equator

Phys. Rev. 80, 47 – Published 1 October 1950
S. F. Singer


Directional intensities and the primary specific ionization of the charged cosmic-ray flux above the atmosphere were measured by means of a G-M counter telescope in an Aerobee sounding rocket launched at the geomagnetic equator. The intensity at a zenith angle of 45° averaged over all azimuths, was found to be 0.04 particle sec.-1 cm-2 steradian-1, of which not more than 65 percent can be attributed to primaries, the remainder being due to albedo. The low value (∼40 percent) of the observed east-west asymmetry is most directly explainable in terms of positive proton primaries and a large albedo flux at large zenith angles, although a small contribution of negative primaries cannot be excluded.

The primary specific ionization of the radiation above the atmosphere is found to be essentially the same as that of the sea-level radiation, indicating a predominance of singly charged particles of near minimum ionization. This result strongly suggests that the albedo radiation at the equator does not consist of low energy (<100 Mev) protons.

Most of the properties of bursts produced in a small lead block can be accounted for reasonably in terms of known initiating particles and interactions.


  • Received 9 June 1950
  • Published in the issue dated October 1950

© 1950 The American Physical Society

Authors & Affiliations

S. F. Singer

  • Applied Physics Laboratory, Johns Hopkins University, Silver Spring, Maryland

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