Consequences of the common origin of the knee and ankle in Cosmic Ray Physics

The differential energy spectrum of the cosmic radiation from solar modulation energies up to 5×1019 eV is correctly predicted by a recent theory of the knee and ankle which uses only one normalization point. This remarkable quantitative result, spanning over many decades in energy and intensity, along with the existence of the second knee at 6×1017 eV, is obtained assuming constant spectral indices of individual ions at the cosmic-ray sources and no other critical hypotheses. In this study the chemical composition of the cosmic radiation is evaluated as a direct consequence of the theory. The computed mean logarithmic mass exhibits a rising trend from 1.8 to 3.0 in the range 1015–1017eV, a maximum value of 3.2 at 3×1017 eV, and a characteristic lightening above 3×1017 eV up to 4×1018 eV. All of these distinctive features are in accord with the data of many experiments. Two additional consequences intrinsic to the theory are qualitatively discussed: (1) some limitative bounds on the mechanism accelerating cosmic rays; (2) the degree of isotropy implied by the residence time of the cosmic rays in the Galaxy.