Monthly Notices of the Royal Astronomical Society, ( ISI ), Volume (419), No (4), Year (2012-8) , Pages (2893-2899)

Title : ( An r-mode in a magnetic rotating spherical layer: application to neutron stars )

Authors: Shahram Abbassi , Michel Rieutord , Vahid Rezania ,

Citation: BibTeX | EndNote

Abstract

The combined impact of rotation and magnetic fields on oscillations of stellar fluids is still not well known theoretically. It mixes Alfv´en and inertial waves. Neutron stars are a place where both effects may be at work. We aim to solve this problem in the context of the r-mode instability in neutron stars, as it appears when these modes are coupled to gravitational radiation.We consider a rotating spherical shell filled with a viscous fluid of infinite electrical conductivity and analyse propagation of model perturbations when a dipolar magnetic field is bathing the fluid layer. We perform an extensive numerical analysis and find that the m =2 r-mode oscillation is influenced by the magnetic field when the Lehnert number (the ratio of Alfv´en speed to rotation speed) exceeds a value proportional to the one-fourth power of the Ekman number (a non-dimensional measure of viscosity). This scaling is interpreted as the coincidence of the width of internal shear layers of inertial modes and the wavelength of the Alfv´en waves. Applied to the case of rotating magnetic neutron stars, we find that dipolar magnetic fields above 1014 G are necessary to perturb the r-mode instability.

Keywords

MHD – stars: magnetic fields – stars: oscillations
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@article{paperid:1046494,
author = {Abbassi, Shahram and Michel Rieutord and Vahid Rezania},
title = {An r-mode in a magnetic rotating spherical layer: application to neutron stars},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2012},
volume = {419},
number = {4},
month = {August},
issn = {0035-8711},
pages = {2893--2899},
numpages = {6},
keywords = {MHD – stars: magnetic fields – stars: oscillations},
}

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%0 Journal Article
%T An r-mode in a magnetic rotating spherical layer: application to neutron stars
%A Abbassi, Shahram
%A Michel Rieutord
%A Vahid Rezania
%J Monthly Notices of the Royal Astronomical Society
%@ 0035-8711
%D 2012

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