Inferring Stellar Magnetic Fields with Magnetic - Internal Gravity Wave Interactions

The brightness of stars varies with time. This is often due to the waves which propagate within stars. It is easy to measure the standing modes of stars because they oscillate at a specific frequency. Here we consider how a standing internal gravity wave may change in the presence of a magnetic field. For weak magnetic field strengths, the wavelength of the internal gravity changes, which would lead to a modification of the frequency of the standing mode. For strong magnetic field strengths, the internal gravity wave converts into a resonant Alfven waves. These resonant waves form a continuum, and the converted mode would likely strongly damp due to phase mixing. Thus, we predict strong magnetic fields will preclude internal gravity wave standing modes. We apply this reasoning to a specific star which does not have as many standing modes as expected. We can explain the lack of standing modes if the star has a strong magnetic field near its convective core.