The University of Southampton
University of Southampton Institutional Repository

Lagrangian perturbation theory for rotating magnetic stars

Lagrangian perturbation theory for rotating magnetic stars
Lagrangian perturbation theory for rotating magnetic stars
Motivated by the possibility of radiation-driven instabilities in rotating magnetic stars, we study the stability properties of general linear perturbations of a stationary and axisymmetric, infinitely conducting perfect fluid configuration threaded by a magnetic field and surrounded by vacuum. We develop a Lagrangian perturbation framework which enables us to formulate a strict stability criterion based on the notion of a canonical energy (a functional of the fluid displacement ? and its first time-derivative). For any given choice of {?, ?t?}, the sign of the canonical energy determines whether the configuration is stable or not at the linear level. Our analysis provides the first complete description of the stability problem for a magnetic star, allowing for both rotation and the presence of a magnetic field in the exterior vacuum region. A key feature of the Lagrangian formulation is the existence of so-called ‘trivial’ fluid displacements, which do not represent true physical perturbations. In order for the stability criterion to make rigorous sense, one has to isolate these trivials and consider only the physical ‘canonical’ displacements. We discuss this problem and formulate a condition which must be satisfied by all canonical displacements. Having obtained a well-defined stability criterion, we provide examples which indicate that the magnetic field has a stabilizing effect on radiation-driven instabilities.
0035-8711
630-644
Glampedakis, Kostas
a08893ef-dd87-4ccb-9d65-3fd6c40fccca
Andersson, Nils
2dd6d1ee-cefd-478a-b1ac-e6feedafe304
Glampedakis, Kostas
a08893ef-dd87-4ccb-9d65-3fd6c40fccca
Andersson, Nils
2dd6d1ee-cefd-478a-b1ac-e6feedafe304

Glampedakis, Kostas and Andersson, Nils (2007) Lagrangian perturbation theory for rotating magnetic stars. Monthly Notices of the Royal Astronomical Society, 377 (2), 630-644. (doi:10.1111/j.1365-2966.2007.11625.x).

Record type: Article

Abstract

Motivated by the possibility of radiation-driven instabilities in rotating magnetic stars, we study the stability properties of general linear perturbations of a stationary and axisymmetric, infinitely conducting perfect fluid configuration threaded by a magnetic field and surrounded by vacuum. We develop a Lagrangian perturbation framework which enables us to formulate a strict stability criterion based on the notion of a canonical energy (a functional of the fluid displacement ? and its first time-derivative). For any given choice of {?, ?t?}, the sign of the canonical energy determines whether the configuration is stable or not at the linear level. Our analysis provides the first complete description of the stability problem for a magnetic star, allowing for both rotation and the presence of a magnetic field in the exterior vacuum region. A key feature of the Lagrangian formulation is the existence of so-called ‘trivial’ fluid displacements, which do not represent true physical perturbations. In order for the stability criterion to make rigorous sense, one has to isolate these trivials and consider only the physical ‘canonical’ displacements. We discuss this problem and formulate a condition which must be satisfied by all canonical displacements. Having obtained a well-defined stability criterion, we provide examples which indicate that the magnetic field has a stabilizing effect on radiation-driven instabilities.

This record has no associated files available for download.

More information

Published date: May 2007

Identifiers

Local EPrints ID: 48199
URI: http://eprints.soton.ac.uk/id/eprint/48199
ISSN: 0035-8711
PURE UUID: 00bba7bf-9122-4747-8a17-54cd67039ad2
ORCID for Nils Andersson: ORCID iD orcid.org/0000-0001-8550-3843

Catalogue record

Date deposited: 04 Sep 2007
Last modified: 09 Jan 2022 02:57

Export record

Altmetrics

Contributors

Author: Kostas Glampedakis
Author: Nils Andersson ORCID iD

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×