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Oscillations and instabilities in neutron stars with poloidal magnetic fields

Oscillations and instabilities in neutron stars with poloidal magnetic fields
Oscillations and instabilities in neutron stars with poloidal magnetic fields
We study the time evolution of non-axisymmetric linear perturbations of a rotating magnetized neutron star, whose magnetic field is purely poloidal. The background stellar configurations are generated self-consistently, with multipolar field configurations and allowing for distortions to the density distribution from rotational and magnetic forces. The perturbations split into two symmetry classes, with perturbations in one class being dominated by an instability generic to poloidal fields, which is localized around the ‘neutral line’ where the background field vanishes. Rotation acts to reduce the effect of this instability. Perturbations in the other symmetry class do not suffer this instability and in this case we are able to resolve Alfvén oscillations, whose restoring force is the magnetic field; this is the first study of non-axisymmetric Alfvén modes of a star with a poloidal field. We find no evidence that these modes form a continuum. In a rotating magnetized star, we find that there are no pure Alfvén modes or pure inertial modes, but hybrids of these. We discuss the nature of magnetic instabilities and oscillations in magnetars and pulsars, finding the dominant Alfvén mode from our simulations has a frequency comparable with observed magnetar quasi-periodic oscillations (QPOs).

instabilities, mhd, stars, magnetic field, neutron, oscillations, rotation
0035-8711
1730-1740
Lander, S.K.
2cad9dc5-3e37-44ed-8ffc-009e7daba257
Jones, D.I.
b8f3e32c-d537-445a-a1e4-7436f472e160
Lander, S.K.
2cad9dc5-3e37-44ed-8ffc-009e7daba257
Jones, D.I.
b8f3e32c-d537-445a-a1e4-7436f472e160

Lander, S.K. and Jones, D.I. (2010) Oscillations and instabilities in neutron stars with poloidal magnetic fields. Monthly Notices of the Royal Astronomical Society, 412 (3), 1730-1740. (doi:10.1111/j.1365-2966.2010.18009.x).

Record type: Article

Abstract

We study the time evolution of non-axisymmetric linear perturbations of a rotating magnetized neutron star, whose magnetic field is purely poloidal. The background stellar configurations are generated self-consistently, with multipolar field configurations and allowing for distortions to the density distribution from rotational and magnetic forces. The perturbations split into two symmetry classes, with perturbations in one class being dominated by an instability generic to poloidal fields, which is localized around the ‘neutral line’ where the background field vanishes. Rotation acts to reduce the effect of this instability. Perturbations in the other symmetry class do not suffer this instability and in this case we are able to resolve Alfvén oscillations, whose restoring force is the magnetic field; this is the first study of non-axisymmetric Alfvén modes of a star with a poloidal field. We find no evidence that these modes form a continuum. In a rotating magnetized star, we find that there are no pure Alfvén modes or pure inertial modes, but hybrids of these. We discuss the nature of magnetic instabilities and oscillations in magnetars and pulsars, finding the dominant Alfvén mode from our simulations has a frequency comparable with observed magnetar quasi-periodic oscillations (QPOs).

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More information

Published date: April 2010
Keywords: instabilities, mhd, stars, magnetic field, neutron, oscillations, rotation
Organisations: Applied Mathematics

Identifiers

Local EPrints ID: 181519
URI: http://eprints.soton.ac.uk/id/eprint/181519
ISSN: 0035-8711
PURE UUID: ca083c65-85af-45da-9730-1ebc4c3aca2b
ORCID for D.I. Jones: ORCID iD orcid.org/0000-0002-0117-7567

Catalogue record

Date deposited: 18 Apr 2011 10:56
Last modified: 08 Jan 2022 02:50

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Contributors

Author: S.K. Lander
Author: D.I. Jones ORCID iD

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