The Internal Structure of the Sun, its Pulsations and the Neutrino Problem

Abstract

The theory of the internal structure of the Sun is described. The standard models of the Sun predict a neutrino flux which is three time larger than that measured by Davis experiment. It is not clear whether this dramatic discrepancy depends on the ideas of stellar structure and evolution theory or on neutrino physics. A convincing attempt to reconcile theory and observations has been done constructing a solar model with a very low primordial abundance of heavy elements. This model predicts the correct neutrino flux, but has a convective zone much thinner than that of the standard model. The observed spectrum of 5 minute oscillations, which is extremely sensitive to the depth of the convection zone, can only be reproduced by the standard model indicating that neutrino flux is high. In recent times, a series of independent experiments have not excluded the possibility that neutrino is massive and oscillates in three different types. Should this be the case, assuming and equally probable mixure of the three neutrinos, the experiment of Davis should actually detect one third of the neutrino flux produced by the Sun at the Earth’s surface.