Knowledge of the chemical composition is fundamental to understanding the origin, acceleration and propagation of cosmic rays. At energies much above 1014 eV, however, the detection of single primary cosmic rays is at present impossible because of their low flux, and the only source of information is from the cascades initiated by energetic primary particles in the atmosphere–the extensive air showers (EAS). A similar situation exists for the study of hadronic interactions above 1015 eV. A recent EAS experiment (Goodman et al., 1979) suggests the possibility that the spectrum becomes increasingly rich in heavy nuclei as the total energy per nucleus approaches 1015 eV. Above that energy the overall spectrum steepens and the question of composition is almost completely open.
Hadronic interactions and cosmic rays at ultra high energies
