Conversion of Internal Waves into Non-Dispersive Waves in Stellar Astrophysics
Orateur :Daniel Lecoanet
Center for Theoretical Science and Department of Astrophysical Sciences, Princeton University
Abstract :
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 the amplitudes of internal gravity waves in red giant branch stars may indicate strong core magnetic fields. Here we present both numerical simulations and analytic calculations of the interactions of internal gravity waves with a strong magnetic field. We can solve the problem very accurately by using the WKB approximation to reduce the non-separable 2D PDE into a series of ODEs for each height. We find that magnetic fields convert the internal gravity waves observable at the surface of the star to magnetic waves, which are not present at the surface, in agreement with observations.
Date et lieu : le Vendredi 15 septembre 2017 à 11h00, salle de séminaire IRPHE