Turbulent mixing problems in RGB stars and white dwarfs

In tropical regions of Earth’s oceans, warm sunshine and surface evaporation create conditions that support a form of turbulence known as double-diffusive convection (DDC). The very same DDC is believed to occur in a variety of stars. In RGB stars, DDC explains an otherwise-perplexing tension between standard stellar models and observations. In polluted white dwarfs, accounting for DDC massively changes the inferred accretion rate needed to explain the observed pollutants. In one formation scenario proposed to explain magnetic white dwarfs, DDC is invoked to explain how magnetic fields are transported from the core to the surface. In each case, we need accurate estimates of DDC-driven mixing in order to properly compare against observations. In this talk, I will summarize these various problems in stellar astrophysics, and provide an update on the state of the art in estimating DDC-driven mixing in these regimes.