Limits on the Spectral shape and Flux of Energetic charged particles from the Proto-Sun

Evidence for the presence of 10 Be (half-life = 1.5 Ma) in the early solar system has been found from studies of primitive meteorites. Interaction of solar energetic particles from the active early Sun with gas and dust present in the solar nebula is considered to be the most plausible source of this nuclide. The presence of 10 Be in meteorite samples is often accompanied by other short-lived nuclides (e.g., 26 Al) for which a stellar origin is generally favored. Our studies show that 10 Be is also present in samples in which 26 Al is below detection level and suggest that the primary source of these two nuclides cannot be the same. This observation places limits on the spectral shape and flux of energetic particles from the proto-Sun such that production of 10 Be is not accompanied by significant production of 26 Al. Our data suggest that the energetic particles from the early Sun were characterized by a hard spectrum and the particle flux was more than 10,000 times the average flux from the contemporary Sun.