On thermonuclear convection: I shellular instability

Abstract

As the sun evolves, a sharp compositional peak of He ³ builds up in the core. Nuclear reactions involving He ³ are very temperature sensitive, as a result, this He ³ layer is susceptible to thermal instability. The small horizontal wavenumber g-modes have large time scales, comparable to the thermal time scale. Using a two-layer model, we find that such “shellular modes” are the most unstable. As a result of nuclear heating, these modes may be excited in the solar core in a shallow layer confined to the He ³ zone. A possible effect of such shellular convection on the solar neutrino problem is discussed. In this paper we discuss the linear theory; the nonlinear effects will be treated in a subsequent paper.