Kostas Glampedakis, Nils Andersson, Samuel K. Lander
Traditionally, the subject of hydromagnetic equilibrium in neutron stars has
been addressed in the context of standard magnetohydrodynamics, with matter
obeying a barotropic equation of state. In this paper we take a step towards a
more realistic treatment of the problem by considering neutron stars with
interior superfluid components. In this multifluid model stratification
associated with a varying matter composition (the relative proton to neutron
density fraction) enters as a natural ingredient, leading to a non-barotropic
system. After formulating the hydromagnetic equilibrium of
superfluid/superconducting neutron stars as a perturbation problem, we focus on
the particular case of a three-fluid system consisting of superfluid neutrons
and normal protons and electrons. We determine the equilibrium structure of
dipolar magnetic fields with a mixed poloidal-toroidal composition. We find
that, with respect to barotropic models, stratification has the generic effect
of leading to equilibria with a higher fraction of magnetic energy stored in
the toroidal component. However, even in models with strong stratification the
poloidal and toroidal components are comparable, with the former contributing
the bulk of the magnetic energy.
View original:
http://arxiv.org/abs/1106.6330
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