The energy distribution below 1 GeV/nucleon of the multiply charged particles of the cosmic rays

The energy spectrum above 200 MeV/nucleon of the heavy (Z≥3) nuclei of the cosmic radiation has been measured in a stack of emulsions flown on the 18-th of September, 1956, at geomagnetic latitude 55° N, and at an atmospheric depth of 6.7 g·cm−2. The total fluxes observed wereJL(0)=4.4±0.8,JM(0)=17.6±2.3, andJH(0)=7.3±1.1 particles m−2s−1sr−1 for the light, medium and heavy nuclei respectively. The energy spectrum of each component exhibited a peak at about 350 MeV/nucleon, and above about 700 MeV/nucleon the spectra were consistent with the usual power law with an exponent γ=2.5. By comparison with the results of other experiments performed under different conditions of solar activity, it is shown that theZ≥3 particle component undergoes a variation in inten sity correlated with that of the ambient cosmic-ray activity recorded by neutron monitors, that a feature of the variation is the stability of the chemical composition of the heavy primary cosmic rays (with the possible exception of the light nuclei), and that the changes of intensity of theZ≥3 component come about chiefly, but not exclusively, through the preferential removal of low energy particles, resulting in a shift of the peak towards higher energies as the flux decreases.