THE PRIMARY COSMIC RADIATION
NAVAL RESEARCH LAB WASHINGTON DC
Pagination or Media Count:
Some salient features of the cosmic radiation incident upon the earth 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 to the 9th power ev per nucleon are 0.28 particle sq cmsec-sterad and 1.2 x 10 to the -10th powercu cm, respectively. The energy density is comparable to that of starlight. NRL measurements indicate that the cosmic-ray abundance of Li, Be, and B at kinetic energies above 1.5 x 10 to the 9th power evnucleon is 2 x 10 to the 5th power 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 sq cm. The relative abundances of the helium isotopes are being investigated as a further means of calculating cosmic-ray path lengths.
- Nuclear Physics and Elementary Particle Physics