METAL ABUNDANCE IN THE SOLAR INTERIOR

It is shown that the metal abundance in the solar interior is constrai ned by the current solar neutrino experiments under the assumption of neutrino conversion in the Sun due to neutrino oscillation via the Mik hyev-Smirnov-Wolfenstein (MSW) effect, the most widely accepted soluti on to the solar neutrino problem. The metal abundance strongly affects the CNO neutrino flux, and an excessive increase of the CNO flux is i ncompatible with the region allowed by the solar neutrino experiments in neutrino-oscillation parameter space. The result shows that the met al abundance in the interior should be within the range 0.5-1.4 times that in the surface, supporting the idea that the Sun formed by a cont raction of a gas cloud with an almost homogeneous composition.