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 , 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