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arXiv · 1412.5852

Magnetically-driven crustquakes in neutron stars

S. K. Lander·N. Andersson·D. Antonopoulou·A. L. Watts
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Abstract

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 $2.4\times 10^{14}$ G for a breaking strain of $0.001$, or $2.4\times 10^{15}$ 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.

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S. K. Lander, N. Andersson, D. Antonopoulou, A. L. Watts. 2015-03-08. Magnetically-driven crustquakes in neutron stars. https://doi.org/10.1093/mnras%2Fstv432

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