On the dynamics of superfluid neutron star cores
Andersson, N. and Comer, G.L. (2001) On the dynamics of superfluid neutron star cores Monthly Notices of the Royal Astronomical Society, 328, (4), p. 1129. (doi:10.1046/j.13658711.2001.04923.x).
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Description/Abstract
We discuss the nature of the various modes of pulsation of superfluid neutron stars using comparatively simple Newtonian models and the Cowling approximation. The matter in these stars is described in terms of a twofluid model, where one fluid is the neutron superfluid, which is believed to exist in the core and inner crust of mature neutron stars, and the other fluid represents a conglomerate of all other constituents (crust nuclei, protons, electrons, etc.). In our model, we incorporate the nondissipative interaction known as the entrainment effect, whereby the momentum of one constituent (e.g. the neutrons) carries along part of the mass of the other constituent. We show that there is no independent set of pulsating gmodes in a nonrotating superfluid neutron star core, even though the linearized superfluid equations contain a welldefined (and realvalued) analogue to the socalled Brunt–Väisälä frequency. Instead, what we find are two sets of spheroidal perturbations whose nature is predominately acoustic. In addition, an analysis of the zerofrequency subspace (i.e. the space of timeindependent perturbations) reveals two sets of degenerate spheroidal perturbations, which we interpret to be the missing gmodes, and two sets of toroidal perturbations. We anticipate that the degeneracy of all these zerofrequency modes will be broken by the Coriolis force in the case of rotating stars. To illustrate this we consider the toroidal pulsation modes of a slowly rotating superfluid star. This analysis shows that the superfluid equations support a new class of rmodes, in addition to those familiar from, for example, geophysical fluid dynamics. Finally, the role of the entrainment effect on the superfluid mode frequencies is shown explicitly via solutions to dispersion relations that follow from a 'local' analysis of the linearized superfluid equations.
Item Type:  Article  

Digital Object Identifier (DOI):  doi:10.1046/j.13658711.2001.04923.x  
ISSNs:  00358711 (print) 

Subjects:  
ePrint ID:  29442  
Date : 


Date Deposited:  12 May 2006  
Last Modified:  16 Apr 2017 22:22  
Further Information:  Google Scholar  
URI:  http://eprints.soton.ac.uk/id/eprint/29442 
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