Modelling heat transport and magnetism in stellar convection zones
Laura Currie (University of Exeter)
Thursday 7th March, 2019 14:00-15:00 Maths 311B
All stars transport some of their energy by convective motions; they are also strongly influenced by (amongst other things) stratification, rotation and magnetism. However, a full understanding of the interaction between convection and such physical effects is lacking. In this talk I will consider a number of idealised numerical models and relevant theory to address a number of open questions. First, convection must be maintained against dissipation. Although the effects of dissipation are often assumed to be negligible, theory suggests that e.g., in strongly stratified convecting fluids, the dissipative heating rate can exceed the luminosity carried by convection. Via a series of simulations under the anelastic approximation we examine the effects of dissipative heating for different stratifications. This has potential implications for the modelling of stellar interiors, where modern standard evolutionary models do not currently allow for dissipative heating. Second, we consider the effect of rapid rotation on convection, in particular its effect on the temperature gradient, and examine whether the results obtained can be understood in terms of a mixing length theory (MLT) framework dating back to Stevenson (1979). Finally, it is widely accepted that astrophysical magnetic fields are generated by dynamo action. Interestingly, in many cases these fields exhibit organisation on a scale larger than that of the underlying turbulent flow. Previous work has shown that in the astrophysically relevant regime, large scale fields are overwhelmed by small scale fluctuating field but that these small scale fluctuations can be suppressed by an imposed shear flow. Here I will examine whether a convective dynamo in which shear is self consistently driven can result in large scale field.