Relative Abundances of Different Charge Groups of Heavy Primary Cosmic-Ray Nuclei

Abstract

SINCE the discovery in 1948¹ that primary cosmic rays entering the Earth's atmosphere contain nuclei of elements ranging in size up to iron, many measurements have been made to establish the charge distribution of the primary radiation. Knowledge of this distribution is of crucial importance for astrophysical investigations into the origin of cosmic rays. There is agreement between different laboratories regarding the flux of nuclei of medium charge, M nuclei, but disagreement on the flux of both light (L) (3≤Z≤5) and heavy (H) (Z > 10) charge groups. Figures given for the relative primary abundances of L and M nuclei exhibit a particularly wide spread, for L/M ranges from < 0.1 to > 1.0. The spread in published values of the heavy-to-medium ratio is less, 0.2 to 0.5, but enough to make further work necessary.