Stably stratified magnetized stars in general relativity

TL;DR

This paper constructs models of stably stratified, magnetized stars in general relativity, demonstrating that combined poloidal and toroidal magnetic fields with stratification can enhance stability against magnetic buoyancy instabilities.

Contribution

It introduces new relativistic star models with stable stratification and mixed magnetic fields, improving upon previous models by addressing stability issues.

Findings

Models include both poloidal and toroidal magnetic fields with comparable strength.

Stratification suppresses magnetic buoyancy instabilities near the surface.

Proposed models are more stable than previous relativistic magnetized star models.

Abstract

We construct magnetized stars composed of a fluid stably stratified by entropy gradients in the framework of general relativity, assuming ideal magnetohydrodynamics and employing a barotropic equation of state. We first revisit basic equations for describing stably-stratified stationary axisymmetric stars containing both poloidal and toroidal magnetic fields. As sample models, the magnetized stars considered by Ioka and Sasaki (2004), inside which the magnetic fields are confined, are modified to the ones stably stratified. The magnetized stars newly constructed in this study are believed to be more stable than the existing relativistic models because they have both poloidal and toroidal magnetic fields with comparable strength, and magnetic buoyancy instabilities near the surface of the star, which can be stabilized by the stratification, are suppressed.