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

Lander, S. K. and Gourgouliatos, K. N. (2019) Magnetic-field evolution in a plastically failing neutron-star crust. Monthly Notices of the Royal Astronomical Society, 486 (3). pp. 4130-4143. ISSN 0035-8711

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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 cms. We find significant motion at the surface at a rate of 10-100 cm yr, 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.

Item Type: Article
Uncontrolled Keywords: stars: evolution,stars: magnetic fields,stars: neutron,astronomy and astrophysics,space and planetary science ,/dk/atira/pure/subjectarea/asjc/3100/3103
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Depositing User: LivePure Connector
Date Deposited: 28 Jan 2020 03:52
Last Modified: 28 Jan 2020 03:52
URI: https://ueaeprints.uea.ac.uk/id/eprint/73798
DOI: 10.1093/mnras/stz1042

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