THE PRIMARY COSMIC RADIATION
Some salient features of the cosmic radiation incident upon the earth are given, and implications of the Li--Be--B anomaly and the helium isotope abundances are discussed. The abundance ratio of cosmic-ray hydrogen to helium is similar to that for the thermal abundances in the sun and nearby stars. The other nuclei, particularly Li, Be, and B, are overabundant relative to hydrogen. Lower limits of cosmic-ray-particle flux and density for total energies exceeding 1.7 x 10/sup 9/ ev per nucleon are 0.28 particle/cm/sup 2/sec-sterad and 1.2 x 10/ sup -10//cm/sup 3/, respectively. The energy density is comparable to that of starlight. Over a wide range of energies, the energy spectrum conforms to a power law in W, the total energy per nucleon: the integral directional intensity varies as W/sup -1.5/. Above 10/sup 14/ ev the spectrum appears steeper, but its exact shape is as yet uncertain. The largest air shower reported came from a particle of an estimated 6 x 10/sup 19/ ev. For a galactic magnetic field of 3 x 10/sup -6/ gauss, such particles would escape from the galaxy. Measurements indicate that the cosmic-ray abundance of Li, Be, and B at kinetic energies above 1.5 x 10/sup 9/ ev/nucleon is 2 x 10/sup 5/ times their general abundance. An assumption that this overabundance arises from the breakup of heavier nuclei permits estimates of the amount of interstellar hydrogen traversed, one estimate being 2.5 g/cm/sup 2/. The relative abundances of the helium isotopes are being investigated as a further means of calculating cosmic-ray path lengths. (auth)
- Research Organization:
- Naval Research Lab., Washington, D.C.; and Weizmann Inst. of Science, Rehovoth, Israel
- NSA Number:
- NSA-17-026267
- OSTI ID:
- 4696872
- Report Number(s):
- NRL-5896; AD-404746
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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