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Magnetic-field evolution in a plastically failing neutron-star crust

Lander, SK; Gourgouliatos, KN

Magnetic-field evolution in a plastically failing neutron-star crust Thumbnail


Authors

SK Lander

KN Gourgouliatos



Abstract

Under normal conditions in a neutron-star (NS) crust, ions are locked in place in the crustal lattice and only electrons are mobile, and magnetic-field evolution is thus directly related to the electron velocity. The evolution, however, builds magnetic stresses that can become sufficiently large for the crust to exceed its elastic limit, and to flow plastically. We consider the nature of this plastic flow and the back-reaction on the crustal magnetic-field evolution. We formulate a plane-parallel model for the local failure, showing that surface motions are inevitable once the crust yields, in the absence of extra dissipative mechanisms. We perform numerical evolutions of the crustal magnetic field under the joint effect of Hall drift and Ohmic decay, tracking the build-up of magnetic stresses, and diagnosing crustal failure with the von Mises criterion. Beyond this point we solve for the coupled evolution of the plastic velocity and magnetic field. Our results suggest that to have a coexistence of a magnetar corona with small-scale magnetic features, the viscosity of the plastic flow must be roughly 1036–1037 g cm−1s−1. We find significant motion at the surface at a rate of 10–100 cm yr−1, and that the localized magnetic field is weaker than in evolutions without plastic flow. We discuss astrophysical implications, and how our local simulations could be used to build a global model of field evolution in the NS crust.

Citation

Lander, S., & Gourgouliatos, K. (2019). Magnetic-field evolution in a plastically failing neutron-star crust. Monthly Notices of the Royal Astronomical Society, 486(3), 4130-4143. https://doi.org/10.1093/mnras/stz1042

Journal Article Type Article
Acceptance Date Apr 10, 2019
Online Publication Date Apr 12, 2019
Publication Date Apr 12, 2019
Deposit Date Jul 30, 2019
Publicly Available Date Jul 30, 2019
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 486
Issue 3
Pages 4130-4143
DOI https://doi.org/10.1093/mnras/stz1042

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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.





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