On the dynamics of mechanical failures in magnetized neutron-star crusts

TL;DR

This paper investigates how strong magnetic fields in neutron-star crusts influence mechanical failures, revealing that magnetic forces prevent large-scale cracks and instead cause slow, plastic deformation, limiting energy release during failures.

Contribution

It demonstrates that magnetic fields in neutron-star crusts inhibit large crack formation and induce plastic deformation, altering the understanding of crustal failure dynamics.

Findings

Magnetic fields prevent large relative displacements during crust failure.

Crustal evolution proceeds on a slow resistive timescale.

Magnetic forces can cause plastic deformation instead of large cracks.

Abstract

We consider the dynamics of a mechanical failure induced by a shear stress in a strongly magnetized neutron-star crust. We show that even if the elastic properties of the crust allow the creation of a shear crack, the strongly sheared magnetic field around the crack leads to a back-reaction from the Lorentz force which does not allow large relative displacement of the crack surfaces. Instead, the global evolution of the crack proceeds on a slow resistive time scale, and is unable to release any substantial mechanical energy. Our calculations demostrate that for {\it some} magnetic-field configurations, the magnetic forces cause, effectively, a plastic deformation of the crust when the resulting elastic shear stress exceeds the critical value for mechanical failure.