Speaker: Adrian Fraser, University of Colorado - Boulder
Abstract: In tropical regions of the Atlantic Ocean, the sun heats and evaporates water off the ocean’s surface, leaving water that’s hotter and saltier than deeper layers. While these gradients don’t drive overturning convection or Rayleigh-Taylor instabilities, they do drive a form of turbulence known as Double-Diffusive Convection (DDC), which regulates heat and salinity transport in many parts of the ocean. I will discuss how analogous conditions in stellar interiors also drive DDC, which may regulate the transport of different chemical species between the envelopes and cores of a broad range of stars. There, stellar magnetic fields can have an enormous impact on the nature and efficiency of this mixing and may resolve a decades-long tension over whether observed mixing signatures are indeed explained by DDC. I will present a suite of MHD simulations that informed our reduced model for predicting this mixing efficiency, and discuss ongoing efforts to check whether MHD DDC indeed solves any stellar chemical mixing problems.