Measurement of hydrogen nuclei in primary cosmic rays

Abstract

The isotopic composition and the energy spectrum of singly charged particles of low energy were analysed using the emulsion stack which was launched on September 4, 1959 from Sioux Falls, S.D. (geomagnetic latitude ~ 53.5 °N) and floated for 8.8 hours under 2.0 g cm°-2 of residual atmosphere and materials. The grain densityvs. range method and the multiple scattering method were used for identification of particles. Fluxes of primary protons and deuterons at the top of the atmosphere are (0.22±0.02) protons m2 s1 sr1 MeV-1 for the kinetic energy range of 82 to 305 MeV for protons, and (0.020±0.008) deuterons m-2 s-1sr-1 (MeV/nucleon)-1 for 56 to 200 MeV/nucleon for deuterons, respectively. The differential energy spectrum of primary protons is given by E-(1.2±0.2). On the basis of the experimental results the possibility of the following origins is discussed: 1) galactic cosmic rays, 2) re-entrant albedo particles, 3) solar particles, and 4) particles from the inner Van Allen radiation belt. It seems to be probable that the particles observed are partly due to those leaked from the inner radiation belt by the distortion of the earth’s magnetic field, although low energy galactic cosmic rays and solar particles may be a part of them.