Cleo (Shyeh Tjing) Loi (Cambridge): Magneto-gravity waves in red giant stars: a 3D ray tracing study
Stars are fluid bodies in which many kinds of waves can propagate. The constructive interference of these waves gives rise to global modes of oscillation, the frequencies of which depend on the interior properties of the star. With the aid of sufficiently sensitive photometry, these oscillations can and have been detected in many distant stars, giving rise to the field of asteroseismology. Analysis of these signals, combined with a theoretical understanding of wave propagation, provides a wealth of information about stellar interiors not obtainable through other means.
In this talk, I discuss a problem in observational asteroseismology involving dipole oscillation modes having amplitudes too low to be explained by standard theory (the "dipole dichotomy" problem). This phenomenon occurs selectively in red giant stars previously thought to have generated a magnetic field inside their cores. Using ray tracing techniques, I present a theoretical study of wave propagation inside red giant cores harbouring magnetic fields, examining the effect of various parameters including wave frequency, field strength and evolutionary state. The predictions of the theory match many aspects of the observations, suggesting that magnetic fields may be a viable explanation for the dipole dichotomy problem.