Solar gravity modes as a test of turbulent diffusion mixing

Abstract

The Stanford group¹ has recently detected solar global oscillations in the range 160–370 min and interpreted them as internal gravity modes of degree l = 1 and l = 2. Other observations^2,3 also indicate the existence of low-degree solar gravity modes. Whereas the high-degree 5-min oscillations are sensitive to the properties of the convective zone essentially, the low-frequency modes (gravity modes) are sensitive to the physical conditions in the solar core. Other constraints on the solar core are given by the observed value of the neutrino flux, which is lower than the flux predicted by the standard models, and by the splitting of the low-degree 5-min oscillations. As far as the neutrino flux is concerned, a possibility to reduce it has been explored by Schatzman and Maeder⁴ by introducing a turbulent diffusion mixing. In this paper we study the influence of such mixing on the periods of low-degree l gravity modes, which do not present the difficulties of the high-degree gravity modes⁵. We find that these periods depend strongly on the pseudo-Reynolds number⁴, and we derive the range of this parameter compatible with the recent observational results.