The stability of poloidal magnetic fields in rotating stars

Understand

The stability of large-scale magnetic fields in rotating stars is explored, using 3D numerical hydrodynamics to follow the evolution of an initial poloidal field.

• It is found that the field is subject to an instability, located initially on the magnetic equator, whereby the gas is displaced in a direction parallel to the magnetic axis.
• If the magnetic axis is parallel to the rotation axis, the rotation does not affect the initial linear growth of the instability, but does restrict the growth of the instability outside of the equatorial zone.
• The magnetic energy decays on a timescale which is a function of the Alfv\'en crossing time and the rotation speed, but short compared to any evolutionary timescale.