Cosmic radiation: The primary particles

Observations of primary cosmic-ray particles entering the upper atmosphere show that the solar system is situated in an isotropic flow of protons and of heavier nuclei, and that these particles carry energy which can vary from small values to values so great that we cannot at present define the upper limit of energy carried by a single particle.

These primary particles are constrained to diffuse through the galaxy as if in a reservoir and must initially have been injected into the reservoir from specific sources. In many ways the turbulent clouds which remain at the site of eruption of supernovae meet the requirements of such sources, and this property can be related to the identification of these objects as sources of strong radio-emission or radio-stars.