Description:

Daniel Lecoanet (Princeton University)

Hosts: Yoram Lithwick

Measuring Core Stellar Magnetic Fields using Wave Conversion

By studying oscillation modes at the surface of stars, astrophysicists are able to infer characteristics of their deep interior structure. This was first applied to observations of the Sun, but recently space-based telescopes have measured oscillations in many other stars, leading to new mysteries in stellar structure and evolution. Recent work has suggested that low dipole oscillation amplitudes in red giant branch stars may indicate strong core magnetic fields. Here we present both numerical simulations and analytic calculations of the interactions of waves with a strong magnetic field. We can solve the problem very accurately by using the WKB approximation to reduce the 2D PDE into a series of ODEs for each height. We find that magnetic fields convert the buoyancy-driven waves observable at the surface of the star to magnetic waves, which are not present at the surface, in agreement with observations.