Quasi-biennial variation of the solar neutrino flux and solar activity

Abstract

THE observed flux of the solar neutrinos is lower by a factor of five than that theoretically estimated from the study of the standard model of the solar interior1. To explain this discrepancy various theories have been proposed which disregard some of the assumptions inherent in this model. However, no theory has been able to reduce the theoretical fluxes to the observed ones2,3. The experimental data obtained by Davis et al.1 indicate that this discrepancy is real, so that these data should be seriously considered in any future research on the solar neutrinos. They have published these data for each period that they have observed since 1968, (Fig. 1)4,5. We have used their data on the solar neutrino fluxes since 1968 to study whether the neutrino flux has any tendency to vary periodically during the solar cycle of 11 yr. The dependence of the neutrino flux on the solar activity, namely, the phase of the solar cycle, was suggested by Sheldon6. He explained that, in the late 1960s, the neutrino production rate in the solar core seemed to be dependent on the degree of the solar activity, as he could only refer to the early results on the neutrino flux observations. It isshown here that this idea is not supported by the data on the neutrino flux obtained since 1968.