Magnetically-driven crustquakes in neutron stars
Dec 18, 201412 pages
Published in:
- Mon.Not.Roy.Astron.Soc. 449 (2015) 2, 2047-2058
- Published: May 11, 2015
e-Print:
- 1412.5852 [astro-ph.HE]
DOI:
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Abstract: (Oxford University Press)
Crustquake events may be connected with both rapid spin-up ‘glitches’ within the regular slowdown of neutron stars, and high-energy magnetar flares. We argue that magnetic-field decay builds up stresses in a neutron star's crust, as the elastic shear force resists the Lorentz force's desire to rearrange the global magnetic-field equilibrium. We derive a criterion for crust-breaking induced by a changing magnetic-field configuration, and use this to investigate strain patterns in a neutron star's crust for a variety of different magnetic-field models. Universally, we find that the crust is most liable to break if the magnetic field has a strong toroidal component, in which case the epicentre of the crustquake is around the equator. We calculate the energy released in a crustquake as a function of the fracture depth, finding that it is independent of field strength. Crust-breaking is, however, associated with a characteristic local field strength of 2.4 × 10^14 G for a breaking strain of 0.001, or 2.4 × 10^15 G at a breaking strain of 0.1. We find that even the most luminous magnetar giant flare could have been powered by crustal energy release alone.Note:
- 13 pages, 8 figures. Minor changes to match MNRAS-accepted version
- asteroseismology
- stars: magnetars
- stars: magnetic field
- stars: neutron
References(85)
Figures(8)