Simulations of Flux Emergence in Stellar Interiors: Toward Linking Dynamo Action with Starspots
Dr Maria Weber (University of Exeter)
Physics, room 3.34
Starspots are windows into a star’s internal dynamo mechanism. They encode information about the generation of stellar magnetic fields, their rise to the surface, and the subsurface flows they encounter. However, the manner by which this magnetism traverses the stellar interior to emerge at the surface is not especially well understood. In the solar context, often the flux tube model is invoked to describe the evolution of rising magnetic field bundles. A rich body of work applying this model in the Sun has provided important insight into the flux emergence process, replicating may observed features of active regions. Here, we review the fundamental nature of dynamo processes in cool, low mass stars and present the results of our flux emergence simulations representative of (1) the Sun, (2) a solar-like rapid rotator, and (3) a fully convective M dwarf. Our simulations utilize the effectively 1D thin flux tube approximation, capturing the global effects of convection on rising flux tubes while circumventing the problem of numerical diffusion common among 3D models. We comment on the ability of our solar simulations to reproduce sunspot observables such as emergence latitude, tilt angles following the Joy’s Law trend, and a phenomenon akin to active longitudes. Further, we compare the evolution of rising flux tubes in our (computationally inexpensive) flux tube simulations to buoyant magnetic structures that arise naturally in global simulations of rapidly rotating convective dynamos. Both computational models complement each other, and demonstrate that convective motions and magnetic buoyancy work in concert to promote flux emergence. In our fully convective M dwarf simulations, the emer
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