Abstract
THE recent advent of artificial satellites has made it possible to measure cosmic ray intensities at energies less than 50 MeV in the vicinity of the Earth. The fluxes of these cosmic ray protons and heavier nuclei are, however, not known in interstellar space, because the reduction of intensity during traversal against the solar wind from the edge of the solar system to the Earth is not known. I use the observations on extraterrestrial background gamma radiation between 0.3 and 2 MeV to set upper limits for cosmic ray protons and CNO nuclei in interstellar space, and I use these values to indicate the nature of solar modulation at low energies.
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APPARAO, M. Upper Limits on Low Energy Cosmic Ray Protons and Heavy Nuclei in Interstellar Space. Nature 220, 1015–1016 (1968). https://doi.org/10.1038/2201015a0
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DOI: https://doi.org/10.1038/2201015a0
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