10:15 AM - 10:30 AM
[SIT03-20] On the origin of a stably stratified layer below the CMB inferred from dynamo models
Keywords:dynamo, core, stable stratification, double diffusive convection
Apart from double diffusive convection, it is inferred from seismic observations that there is a thin stably stratified layer of O(100) km below the core-mantle boundary. However, it is not well constrained whether the origin of stable stratification is thermal or compositional. Here we investigate effects of a stable layer on dynamo action driven by double diffusive convection. Stably stratified layer is imposed by giving a sub-adiabatic temperature gradient. Thickness of the stable layer is assumed to be 10 % of the core radius. It is found that strength of the dynamo-generated magnetic field is significantly reduced by the thin stable layer in case of dipolar dynamos. On the other hand, the magnetic field is strengthened with the stable layer in case of weak multi-polar dynamos, consistent with a previous study. We discuss mechanisms responsible for such a difference and implications for the origin of the stably stratified layer.