Shear Viscosity of the outer crust of Neutron stars: Ion Contribution

TL;DR

This paper investigates the ion contribution to shear viscosity in neutron star crusts, using both semi-analytical methods and molecular dynamics simulations, to understand its impact on r-mode damping and gravitational wave emission.

Contribution

It provides a comparative analysis of ion shear viscosity calculations using semi-analytical and molecular dynamics methods for neutron star crust conditions.

Findings

Good agreement between molecular dynamics and semi-analytical results at low densities.

Shear viscosity depends on density in neutron star crusts.

Ion contribution is significant for r-mode damping.

Abstract

The shear viscosity of the crust might have a damping effect on the amplitude of r-modes of rotating neutron stars. This damping has implications for the emission of gravitational waves. We calculate the contribution to the shear viscosity coming from the ions using both semi-analytical methods, that consider binary collisions, and Molecular Dynamics simulations. We compare these results with the contribution coming from electrons. We study how the shear viscosity depends on density for conditions of interest in neutron star envelopes and outer crusts. In the low density limit, we find good agreement between results of our molecular dynamics simulations and classical semi-analytic calculations.