Non-axisymmetric magnetic modes of neutron stars with purely poloidal magnetic fields

Abstract

We calculate non-axisymmetric oscillations of neutron stars magnetized by purely poloidal magnetic fields. We use polytropes of index $n=1$ and 1.5 as a background model, where we ignore the equilibrium deformation due to the magnetic field. Since separation of variables is not possible for the oscillation of magnetized stars, we employ finite series expansions for the perturbations using spherical harmonic functions. Solving the oscillation equations as the boundary and eigenvalue problem, we find two kinds of discrete magnetic modes, that is, stable (oscillatory) magnetic modes and unstable (monotonically growing) magnetic modes. For isentropic models, the frequency or the growth rate of the magnetic modes is exactly proportional to $B_{\mathrm{S}}$, the strength of the field at the surface. The oscillation frequency and the growth rate are affected by the buoyant force in the interior, and the stable stratification tends to stabilize the unstable magnetic modes.

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Cited by in corpus (7)

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• Quasi-periodic oscillations in superfluid, relativistic magnetars with nuclear pasta phases
• Torsional oscillations and observed rotational period variations in early-type stars
• Oscillations of Highly Magnetized Non-rotating Neutron Stars
• A perturbation study of axisymmetric strongly magnetic degenerate stars : the case of super-Chandrasekhar white dwarfs
• Axisymmetric magnetic modes of neutron stars having mixed poloidal and toroidal magnetic fields
• Axisymmetric spheroidal modes of neutron stars magnetized with poloidal magnetic fields