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Oscillations of rotating magnetized neutron stars with purely toroidal magnetic fields

Oscillations of rotating magnetized neutron stars with purely toroidal magnetic fields
Oscillations of rotating magnetized neutron stars with purely toroidal magnetic fields
We investigate the oscillation spectrum of rotating Newtonian neutron stars endowed with purely toroidal magnetic fields, using a time-evolution code to evolve linear perturbations in the Cowling approximation. The background star is generated by numerically solving the magnetohydrodynamics equilibrium equations and may be non-spherical by virtue of both rotation and magnetic effects; hence, our perturbations and background are fully consistent. Whilst the background field is purely toroidal, the perturbed field is mixed poloidal–toroidal. From Fourier analysis of the perturbations, we are able to identify a number of magnetically restored Alfvén (or a) modes. We show that in a rotating star pure inertial and a-modes are replaced by hybrid magneto-inertial modes, which reduce to a-modes in the non-rotating limit and inertial modes in the non-magnetic limit. We show that the r-mode instability is suppressed by magnetic fields in sufficiently slowly rotating stars. In addition, we determine magnetic frequency shifts in the f-mode. We discuss the astrophysical relevance of our results, in particular for magnetar oscillations.
MHD, stars: magnetic fields, stars: neutron, stars: oscillations, stars: rotation
0035-8711
Lander, S.K.
2cad9dc5-3e37-44ed-8ffc-009e7daba257
Jones, D.I.
b8f3e32c-d537-445a-a1e4-7436f472e160
Passamonti, A.
d9c7544a-5b0e-4230-9caa-f5a9a6fe9f13
Lander, S.K.
2cad9dc5-3e37-44ed-8ffc-009e7daba257
Jones, D.I.
b8f3e32c-d537-445a-a1e4-7436f472e160
Passamonti, A.
d9c7544a-5b0e-4230-9caa-f5a9a6fe9f13

Lander, S.K., Jones, D.I. and Passamonti, A. (2010) Oscillations of rotating magnetized neutron stars with purely toroidal magnetic fields. Monthly Notices of the Royal Astronomical Society. (doi:10.1111/j.1365-2966.2010.16435.x).

Record type: Article

Abstract

We investigate the oscillation spectrum of rotating Newtonian neutron stars endowed with purely toroidal magnetic fields, using a time-evolution code to evolve linear perturbations in the Cowling approximation. The background star is generated by numerically solving the magnetohydrodynamics equilibrium equations and may be non-spherical by virtue of both rotation and magnetic effects; hence, our perturbations and background are fully consistent. Whilst the background field is purely toroidal, the perturbed field is mixed poloidal–toroidal. From Fourier analysis of the perturbations, we are able to identify a number of magnetically restored Alfvén (or a) modes. We show that in a rotating star pure inertial and a-modes are replaced by hybrid magneto-inertial modes, which reduce to a-modes in the non-rotating limit and inertial modes in the non-magnetic limit. We show that the r-mode instability is suppressed by magnetic fields in sufficiently slowly rotating stars. In addition, we determine magnetic frequency shifts in the f-mode. We discuss the astrophysical relevance of our results, in particular for magnetar oscillations.

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Published date: March 2010
Keywords: MHD, stars: magnetic fields, stars: neutron, stars: oscillations, stars: rotation

Identifiers

Local EPrints ID: 151835
URI: http://eprints.soton.ac.uk/id/eprint/151835
ISSN: 0035-8711
PURE UUID: 49c65788-0e95-4a2a-990f-6bb28c4a70d6
ORCID for D.I. Jones: ORCID iD orcid.org/0000-0002-0117-7567

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Date deposited: 12 May 2010 13:23
Last modified: 09 Jan 2022 03:00

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Contributors

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

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