Microphysics of Neutron Star Outer Envelopes in the Periodized, Magnetic Thomas-Fermi Model

Abstract

Static and dynamic properties of low density outer envelopes of neutron stars are calculated within the nonlinear magnetic Thomas-Fermi model, assuming degenerate electrons. A novel domain decomposition enables proper description of lattice symmetry and may be seen as a prototype for the general class of problems involving nonlinear charge screening of periodic, quasi-low-dimensionality structures, e.g. liquid crystals. We describe a scalable implementation of the method using Hypre. Phase velocity of long wavelength transverse phonons is found to be a factor of 5-7 larger than in the corresponding Coulomb crystal model, which could have implications for low temperature phononmediated thermal conductivity. Other findings include c < 0 elastic instabilities for both bcc and fcc lattices, reminiscent of the situation in some light actinides, and suggestive of a symmetry-lowering transition to a tetragonal or orthorhombic lattice.

Crystal Chemistry of Three-Component White Dwarfs and Neutron Star Crusts: Phase Stability, Phase Stratification, and Physical Properties

“…the local magnetic field, would necessitate computing the full elastic tensor. Anisotropies, soft phonon modes, and elastic instabilities such as the incipient ones described in Engstrom et al (2015) could have significant effects on elasticity-related astrophysical observables such as magnetar flares (Perna & Pons 2011), related quasi-periodic oscillations (Israel et al 2005), and possibly some pulsar glitches (Chamel & Haensel 2008). It could also significantly affect the future observability of gravitational-wave emission, both in the context of magnetar flares and continuous waves (Johnson-McDaniel & Owen 2013).…”