The MSW solution to the solar neutrino problem for non-standard solar models

The difficulties for non-standard solar models (NSSM) in resolving the solar neutrino problem are discussed stressing the incompatibility of the gallium-Kamiokande data, and of the gallium-Homestake data. We conclude that NSSMʹs cannot explain simultaneously the results of any two of the solar neutrino data (chlorine, Kamiokande and gallium). We address further the question whether the MSW solution exists for NSSMʹs (e.g. models with 8B neutrino flux much lower than the standard one and/or central temperature Tc very different from TSSMc. We demonstrate the the MSW solution exists and is very stable relative to changes of S17 (S-factor for p+7Be reaction) and Tc. In particular, Δm2 is almost constant, while sin2 2θ depends on the exact values of S17 (or 8B-neutrino flux) and Tc.