Solar models with rotating cores

Abstract

IT is possible to achieve low solar neutrino fluxes with solar models with rapidly rotating cores^1–3. But to achieve a flux consistent with the 1 SNU (1 SNU = 10⁻³⁶ neutrino capture per (target atom s⁻¹) upper limit of Davis⁴, the rotation must be so rapid that the approximate treatment of rotation used is of doubtful validity. Further it is difficult to obtain a result simultaneously giving a flux less than 1 SNU and a solar oblateness consistent with observation⁵. Sakurai⁶ has shown that it is possible for Eddington–Sweet circulation to transfer angular momentum both inwards and outwards in solar models with rotating cores on a time scale much less than the solar lifetime. Thus as the Sun evolves, its rotating core gets smaller while its outer part spins up. This suggestion has led us to investigate the possibility that this spin-up might lead to the onset of some transient phenomenon, such as the sudden beginning of thermal convection. Under special circumstances, a transient state can lead to temporarily depressed neutrino fluxes^7–10. It was hoped that the transient phase induced by spin-up, coupled with an already depressed flux due to the rotating core would lead to a flux of less than 1 SNU while requiring less extreme transients or rotation than is necessary when these effects are applied separately. In addition, a mechanism for the transient would be provided. Unfortunately this hope has not been realised and additional problems with rotating solar models have been discovered.