Instability of Superfluid Flow in the Neutron Star Core
arXiv:1111.0696 · doi:10.1111/j.1365-2966.2012.20498.x
Abstract
Pinning of superfluid vortices to magnetic flux tubes in the outer core of a neutron star supports a velocity difference of \cms\ between the neutron superfluid and the proton-electron fluid as the star spins down. Under the Magnus force that arises on the vortex array, vortices undergo {\em vortex creep} through thermal activation or quantum tunneling. We examine the hydrodynamic stability of this situation. Vortex creep introduces two low-frequency modes, one of which is unstable above a critical wavenumber for any non-zero flow velocity of the neutron superfluid with respect to the charged fluid. For typical pinning parameters of the outer core, the superfluid flow is unstable over wavelengths $λ\lap 10$ m and over timescales of yr down to d. The vortex lattice could degenerate into a tangle, and the superfluid flow would become turbulent. We suggest that superfluid turbulence could be responsible for the red timing noise seen in many neutron stars, and find a predicted spectrum that is generally consistent with observations.
12 pages. Final journal version
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- Evidence for an abundant old population of Galactic ultra long period magnetars and implications for fast radio bursts
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