Torsional seismic vibrations of solid crust in quaking paramagnetic neutron star.
S.I. Bastrukov I.V. Molodtsova H.-K. Chang J. Takata
posted in Astrophysics on Sunday, October 18th, 2009
We investigate an asteroseismic model of non-rotating paramagnetic neutron star with core-crust stratification of interior pervaded by homogeneous internal and dipolar external magnetic field. Focus is on post-quake vibrational relaxation by torsional shear oscillations of electron-nuclear solid-state plasma in the metal-like crust about axis of magnetic field frozen in the immobile core. In accord with basic physics underlying the very notion of a neutron star and indirect observational evidence of the dipole configuration of magnetic fields of pulsars and magnetars, the model under consideration presumes that micro-composition of core material is dominated by degenerate neutron matter in the state of Pauli's paramagnetic permanent magnetization caused by polarizations of spin magnetic moments of neutrons along magnetic axis of the star. Particular attention is given to the regime of node-free differentially rotational vibrations of crust against immobile core driven by Lorentz magnetic and Hooke's elastic forces and damped by Newtonian force of shear viscous stresses. Based on the energy variational method of solid-mechanical theory of elastic continuous medium, the spectral formulae for the frequency and lifetime of this axial toroidal mode are obtained and discussed in the context of current view of quasi-periodic oscillations of the X-ray outburst flux from SGR 1806-20 and SGR 1900+14 as being produced by torsional seismic vibrations of underlying magnetars.
