Alpha Particles in Solar Cosmic Rays over the Last 80,000 Years

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Science  23 Mar 1973:
Vol. 179, Issue 4079, pp. 1232-1234
DOI: 10.1126/science.179.4079.1232


Present-day (1967 to 1969) fluxes of alpha particles from solar cosmic rays, determined from satellite measurements, were used to calculate the production rates of cobalt-57, cobalt-58, and nickel-59 in lunar surface samples. Comparisons with the activities of nickel-59 (half-life, 8 x 104 years) measured in lunar samples indicate that the long-term and present-day fluxes of solar alpha particles are comparable within a factor of approximately 4.