LAUSR

The evolution of a star is influenced by its internal rotation dynamics through transport and mixing mechanisms, which are poorly understood. Magnetic fields can play a role in transporting angular momentum and chemical elements, but the origin of magnetism in radiative stellar layers is unclear. Using global numerical simulations, we identify a subcritical transition from laminar flow to turbulence caused by the generation of a magnetic dynamo. Our results have many properties of the theoretically proposed Tayler-Spruit dynamo mechanism, which strongly enhances transport of angular momentum in radiative zones. The dynamo generates deep toroidal fields that are screened by the stellar outer layers. This mechanism could produce strong magnetic fields inside radiative stars without an observable field on their surface. Description A simulated dynamo in radiative stars Strong stellar magnetic fields are generated by dynamos, which typically require convection of material inside the star. Petitdemange et al. used numerical simulations to show how a stellar dynamo can form in layers that are purely radiative (meaning that they have no convection). Their results matched most of the properties of a theoretical prediction known as the Tayler-Spruit dynamo. The resulting magnetic field remains trapped inside the star, so it would not be observable on the surface but could potentially be inferred using asteroseismology. Because magnetic fields can transport angular momentum, the mechanism slows the spin of stellar cores and increases the rotation of the outer layers, enhancing the mixing of chemical elements. —KTS Simulations of stellar interiors can produce a dynamo that generates a magnetic field without requiring convection.