Speaker: Dr. Adrian E. Fraser
Affiliation: University of Colorado Boulder
Date: Thursday, May 14, 2026
Time: 12:00 PM
Abstract
Stars of all sizes and ages are plagued by "missing mixing problems," or discrepancies between stellar models and observations that indicate some unknown turbulent mixing occurs in their interiors. The precise nature and degree of this anomalous mixing can hold major consequences for the fates of such stars, their spins, and their chemical makeup over time. I will discuss a particularly ubiquitous mixing problem in red giant branch stars—a widely observed class of star that our own sun will eventually become. The leading candidate to explain the missing mixing in these stars is salt-finger (or “thermohaline”) convection, a form of turbulence also found in tropical oceans. I will show that the dynamics of salt fingers in stars are often surprisingly similar to oceans (despite the enormous difference in fluid properties between stellar plasmas and salt water) except when magnetic fields are present. In such cases, magnetic fields dramatically enhance the turbulent mixing rate, potentially solving this long-standing missing mixing problem.