Thermoplastic waves in magnetars

TL;DR

This paper introduces a novel thermoplastic wave mechanism in magnetars, where magnetic stresses induce shear motions through a thermoplastic instability, leading to wave propagation that releases magnetic energy and potentially explains magnetar activity.

Contribution

It proposes a new deformation mechanism specific to strongly magnetized neutron stars involving thermoplastic instability and wave propagation.

Findings

Identifies conditions for thermoplastic instability in magnetar crusts

Describes the structure and velocity of the propagating wave front

Discusses implications for observed magnetar activity

Abstract

Magnetar activity is generated by shear motions of the neutron star surface, which relieve internal magnetic stresses. An analogy with earthquakes and faults is problematic, as the crust is permeated by strong magnetic fields, which greatly constrain crustal displacements. We describe a new deformation mechanism that is specific to strongly magnetized neutron stars. The magnetically stressed crust begins to move because of a thermoplastic instability, which launches a wave that shears the crust and burns its magnetic energy. The propagating wave front resembles the deflagration front in combustion physics. We describe the conditions for the instability, the front structure and velocity, and discuss implications for observed magnetar activity.