New Method Extends Asteroseismic Magnetometry to Complex Magnetic Field Configurations in Red Giants
Researchers have extended a theoretical framework for measuring magnetic fields in red giant star cores to handle arbitrarily shaped, non-axisymmetric magnetic field configurations. Previously, the method was limited to magnetic fields aligned symmetrically around a star's rotation axis. The advance allows astronomers to model more realistic and complex magnetic structures, improving the accuracy of asteroseismic magnetometry across a broader range of stellar environments.
A new study submitted to Monthly Notices of the Royal Astronomical Society extends asteroseismic magnetometry — the technique of measuring stellar magnetic fields through the analysis of oscillation modes — to magnetic field geometries that lack rotational symmetry. The existing formalism, based on the traditional approximation of rotation and magnetism, had previously been restricted to axisymmetric fields aligned with a star's rotation axis. The authors now calculate how magnetogravity waves propagate under arbitrarily shaped fields, including a dipolar field misaligned with the rotation axis and a combined dipole-plus-quadrupole field with no rotational symmetry. A key finding is that non-axisymmetric configurations can induce avoided crossings between wave polarizations and cause waves to convert between magnetogravity polarizations as they travel through the stellar interior. The study also identifies a stratification-dependent threshold field strength — distinct from the previously known critical field for gravity-mode suppression — below which such polarization conversions are especially pronounced and perturbation theory begins to break down. These results are relevant to the many red giants whose core magnetic fields have already been measured, as most prior interpretations assumed simpler field geometries.
What's missing
The study is a preprint submitted to MNRAS and has not yet undergone peer review.
What different sources said
- arXiv astro-phCenter
Extending asteroseismic magnetometry across the diverse landscape of magnetic structures
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