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Plasma Physics (Physics/ECE/NE 922) Seminar
Wave Conversion from Stellar Magnetic Fields
Date: Monday, October 29th
Time: 12:05 pm
Place: 2241 Chamberlin Hall
Speaker: Daniel Lecoanet, Princeton University
Abstract: Stars have global oscillation modes, which can be observed by looking for periodic brightness variations. If many modes of oscillation have been identified, one can infer the properties of the deep interiors of stars. 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 an ODE 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.
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