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Local magneto-shear instability in Newtonian gravity

Local magneto-shear instability in Newtonian gravity
Local magneto-shear instability in Newtonian gravity

The magneto-rotational instability (MRI), which is due to an interplay between a sheared background and the magnetic field, is commonly considered a key ingredient for developing and sustaining turbulence in the outer envelope of binary neutron star merger remnants. To assess whether (or not) the instability is active and resolved, criteria originally derived in the accretion disc literature, thus exploiting the symmetries of such systems, are often used. In this paper, we discuss the magneto-shear instability as a truly local phenomenon, relaxing common symmetry assumptions on the background on top of which the instability grows. This makes the discussion well suited for highly dynamical environments such as binary mergers. We find that, although this is somewhat hidden in the usual deri v ation of the MRI dispersion relation, the instability crucially depends on the assumed symmetries. Relaxing the symmetry assumptions in the background, we find that the role of the magnetic field is significantly diminished, as it affects the modes' growth but does not drive it. We conclude by making contact with a suitable filtering operation, as this is key to separating background and fluctuations in highly dynamical systems.

astro-ph.HE, physics.flu-dyn, physics.plasm-ph, stars: oscillations, instabilities, stars: rotation, stars: neutron
2437-2451
Celora, Thomas
b15e9792-aae0-479a-83c5-b5c874b19fa6
Hawke, Ian
fc964672-c794-4260-a972-eaf818e7c9f4
Andersson, Nils
2dd6d1ee-cefd-478a-b1ac-e6feedafe304
Comer, Gregory L.
844e5be1-aab1-4406-a5c7-951e4988268f
Celora, Thomas
b15e9792-aae0-479a-83c5-b5c874b19fa6
Hawke, Ian
fc964672-c794-4260-a972-eaf818e7c9f4
Andersson, Nils
2dd6d1ee-cefd-478a-b1ac-e6feedafe304
Comer, Gregory L.
844e5be1-aab1-4406-a5c7-951e4988268f

Celora, Thomas, Hawke, Ian, Andersson, Nils and Comer, Gregory L. (2024) Local magneto-shear instability in Newtonian gravity. MNRAS, 527 (2), 2437-2451. (doi:10.1093/mnras/stad2613).

Record type: Article

Abstract

The magneto-rotational instability (MRI), which is due to an interplay between a sheared background and the magnetic field, is commonly considered a key ingredient for developing and sustaining turbulence in the outer envelope of binary neutron star merger remnants. To assess whether (or not) the instability is active and resolved, criteria originally derived in the accretion disc literature, thus exploiting the symmetries of such systems, are often used. In this paper, we discuss the magneto-shear instability as a truly local phenomenon, relaxing common symmetry assumptions on the background on top of which the instability grows. This makes the discussion well suited for highly dynamical environments such as binary mergers. We find that, although this is somewhat hidden in the usual deri v ation of the MRI dispersion relation, the instability crucially depends on the assumed symmetries. Relaxing the symmetry assumptions in the background, we find that the role of the magnetic field is significantly diminished, as it affects the modes' growth but does not drive it. We conclude by making contact with a suitable filtering operation, as this is key to separating background and fluctuations in highly dynamical systems.

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Accepted/In Press date: 24 August 2023
e-pub ahead of print date: 2 September 2023
Published date: 1 January 2024
Additional Information: Funding Information: NA and IH gratefully acknowledge support from Science and Technology Facilities Council (STFC) via grant numbers ST/R00045X/1 and ST/V000551/1. Publisher Copyright: © 2023 The Author(s).
Keywords: astro-ph.HE, physics.flu-dyn, physics.plasm-ph, stars: oscillations, instabilities, stars: rotation, stars: neutron

Identifiers

Local EPrints ID: 486074
URI: http://eprints.soton.ac.uk/id/eprint/486074
PURE UUID: 4c5b0bfc-0920-4590-b5e8-81eb7bc138e4
ORCID for Thomas Celora: ORCID iD orcid.org/0000-0002-6515-3644
ORCID for Ian Hawke: ORCID iD orcid.org/0000-0003-4805-0309
ORCID for Nils Andersson: ORCID iD orcid.org/0000-0001-8550-3843

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Date deposited: 08 Jan 2024 17:52
Last modified: 29 May 2024 01:39

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Contributors

Author: Thomas Celora ORCID iD
Author: Ian Hawke ORCID iD
Author: Nils Andersson ORCID iD
Author: Gregory L. Comer

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