Did solar energetic particles produce the short-lived nuclides present in the early solar system?

Production of the short-lived nuclides Ca-41, Cl-36, Al-26, and Mn-53 by so lar energetic particles (SEP) interacting with dust grains of chondritic (= solar) composition is estimated considering a broad range of spectral param eters for the SEP and appropriate nuclear reaction cross sections. The dust grains are assumed to follow a power-law size distribution and to range in size from 10 mum to 1 cm. The possibility that an enhanced flux of SEP fro m an active early (T Tauri) Sun could have been responsible for the product ion of these short-lived nuclides in the early solar system is investigated . SEP production of Ca-41 and Cl-36 will match their abundances in the earl y solar system inferred from meteorite data if the SEP irradiation duration was similar to5 x 10(5)-10(6) yr and the SEP flux was higher by a factor o f more than 5 x 10(3) than the contemporary long-term averaged value of N-p roton (E > 10 MeV) similar to 100 cm(-2) s(-1). However, corresponding prod uction of Al-26 will be much below the level needed to match its inferred a bundance in the early solar system. SEP production, therefore, fails to exp lain the observed correlated presence of Ca-41 and Al-26 with canonical ini tial abundances in early solar system solids. The abundance of Mn-53 in the early solar system is not tightly constrained by the meteorite data, and t he various estimates differ by a factor of 5. Coproduction of Ca-41, Cl-36, and Mn-53 that will match the meteorite data for the higher initial abunda nce of Mn-53 is possible if the SEP irradiation persisted for about a milli on years or more with a flux enhancement factor of similar to 5000-10,000. On the other hand, the lower initial value of Mn-53 can also be matched by a flux enhancement factor of similar to 1000 and an irradiation duration of a few million years; the corresponding production of the other nuclides wi ll be less than or equal to 10% of the level needed to match their abundanc es in the early solar system. Target abundance consideration rules out the possibility of SEP production of Fe-60, another short-lived nuclide present in the early solar system. Thus, SEP production as the primary source of t he short-lived nuclides in the early solar system appears to be unlikely. H owever, the possibility that SEP production could be an important source of Mn-53 as well as of the short-lived nuclide Be-10, whose presence in the e arly solar system solids has been recently reported, makes it difficult to completely rule out any contribution from this source to the inventory of t hese nuclides in the early solar system.