Instabilities in neutron stars with toroidal magnetic fields

Abstract

We study $m=1$ oscillations and instabilities of magnetised neutron stars, by numerical time-evolution of linear perturbations of the system. The background stars are stationary equilibrium configurations with purely toroidal magnetic fields. We find that an $m=1$ instability of toroidal magnetic fields, already known from local analyses, may also be found in our relatively low-resolution global study. We present quantitative results for the instability growth rate and its suppression by rotation. The instability is discussed as a possible trigger mechanism for Soft Gamma Repeater (SGR) flares. Although our primary focus is evolutions of magnetised stars, we also consider perturbations about unmagnetised background stars in order to study $m=1$ inertial modes. We track these modes up to break-up frequency, extending known slow-rotation results.

9 pages, 8 figures. Very minor changes from v1 and one reference added, to match MNRAS-accepted version

References in corpus (6)

• The strongest cosmic magnets: Soft Gamma-ray Repeaters and Anomalous X-ray Pulsars
• Stability of Toroidal Magnetic Fields in Rotating Stellar Radiation Zones
• Evolution of neutron stars with toroidal magnetic fields: Axisymmetric simulation in full general relativity
• On the trigger mechanisms for SGR giant flares
• Comparative study of the inial spikes of SGR giant flares in 1998 and 2004 observed with GEOTAIL: Do magnetospheric instabilities trigger large scale fracturing of magnetar's crust?
• Lagrangian perturbation theory for rotating magnetic stars

Cited by in corpus (10)

• Magneto-elastic oscillations of neutron stars: exploring different magnetic field configurations
• Stably stratified magnetized stars in general relativity
• Does elasticity stabilise a magnetic neutron star?
• Gravitomagnetic effect in magnetized neutron stars
• Generation of strong magnetic fields by r-modes in millisecond accreting neutron stars: induced deformations and gravitational wave emission
• Magneto-elastic equilibrium of a neutron-star crust
• Accumulation of elastic strain toward crustal fracture in magnetized neutron stars
• Stably stratified stars containing magnetic fields whose toroidal components are much larger than the poloidal ones in general relativity: A perturbation analysis
• Magnetic field sustained by the elastic force in neutron star crusts
• A perturbation study of axisymmetric strongly magnetic degenerate stars : the case of super-Chandrasekhar white dwarfs