On hydrodynamic stability of weakly magnetized stellar radiative zones

Abstract

We consider the stability of weakly magnetized differentially rotating stars to adiabatic axisymmetric disturbances. The general case of the angular velocity being dependent on both the spherical radius and the polar angle is analysed. In magnetized radiative zones, there are two low-frequency modes, the buoyant and torsion Alfvén ones, which can be destabilized by a differential rotation. For instability, the buoyant mode requires a decrease of the specific angular momentum in the direction from the poles to the equator, whereas the Alfvén mode can be unstable if the angular velocity decreases from the poles to the equator. A relatively strong magnetic field may stabilize both of these modes.