Transitions between Turbulent and Laminar Superfluid Vorticity States in the Outer Core of a Neutron Star

Peralta, C.; Melatos, A.; Giacobello, Matteo; Ooi, Andrew

doi:10.1086/507576

Cited by 107 publications

(149 citation statements)

References 119 publications

(166 reference statements)

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“…The time scales of this relaxation, as well as a more detailed analysis of these processes requires further specially targeted investigations. In this context, it is worth noting that our results could offer a microscopic understanding of the physics of superfluid vortex tangle patches of laminar-turbulent transition in neutron stars as discussed by Peralta et al 2006.…”

Section: Resultsmentioning

confidence: 69%

“…A crucial question in statistical theories of thermal superfluid turbulence (Peralta et al 2006(Peralta et al , 2008Andersson et al 2007;Sidery et al 2008) is whether the average (macroscopic) effects of mutual friction could be modelled by an isotropic (Gorter and Mellink) or rectilinear-array-type (Hall & Vinen 1956) laws. The present results suggest that (in homogeneous isotropic turbulence) neither approach is absolutely correct.…”

Section: Resultsmentioning

confidence: 99%

“…Finally, a further coarse-graining of our model would correspond to theories of the HallVinen (Hall & Vinen 1956) and Bekharevich-Khalatnikov (Leggett 2006) type, i.e. to statistical theories of thermal superfluid turbulence (Henderson & Barenghi 2004;Peralta et al 2005Peralta et al , 2006Peralta et al , 2008Andersson, Sidery & Comer 2007;Sidery, Andersson & Comer 2008;Melatos & Peralta 2010). The mathematical difficulties involved in this coarse-graining are great, and our results could guide the relevant analyses.…”

Section: Introductionmentioning

confidence: 85%

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Spreading of superfluid vorticity clouds in normal-fluid turbulence

Kivotides

2010

J. Fluid Mech.

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In this paper, we formulate a self-consistent model of thermal superfluid dynamics. By solving it, we analyse the problem of superfluid vorticity cloud propagation in normal-fluid turbulence. We show that superfluid cloud expansion is driven by pattern-forming superfluid vortex instabilities taking place in the interface layer between the cloud's bulk and the outer undisturbed normal-fluid turbulence. The radius of the cloud increases linearly with time. Mutual friction transfers energy from the normal-fluid turbulence to the superfluid cloud, whilst damping the smallest normal-fluid turbulence motions. This damping action is much weaker than viscous dissipation effects in a corresponding pure normal-fluid turbulence. The energy spectrum of superfluid turbulence presents the k −3 scaling that characterizes the spiral superfluid vorticity patterns of normal vortex tube-superfluid vortex interactions. The corresponding k −2 pressure spectrum signifies the singular nature of superfluid vorticity. These two scalings coincide in wavenumber space with the Kolmogorov regime in the normal-fluid turbulence. We compute a fractal dimension d f ≈ 1.652 for superfluid vorticity. Due to simpler underlying superfluid vortex dynamics in relation to the strongly nonlinear classical vortex dynamics, this fractal dimension is smaller than the corresponding dimension of vortex tube centrelines in classical turbulence.

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Section: Resultsmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 85%

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Spreading of superfluid vorticity clouds in normal-fluid turbulence

Kivotides

2010

J. Fluid Mech.

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“…The simple model above shows that the pinning profiles we have calculated can play a very important role in the study of glitches, and could be used as a background for more realistic glitch models and vortex dynamics simulations (Peralta et al 2006;Haskell, Pizzochero & Sidery 2013;Sidery, Passamonti & Andersson 2010;Warszawski & Melatos 2008, 2011Haskell & Antonopoulou 2013). Note that here we have only calculated the contribution to the pinning force acting on a vortex from the ions in the crust.…”

Section: Application To Pulsar Glitchesmentioning

confidence: 87%

Mesoscopic pinning forces in neutron star crusts

Seveso¹,

Pizzochero²,

Grill³

et al. 2015

Mon. Not. R. Astron. Soc.

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The crust of a neutron star is thought to be comprised of a lattice of nuclei immersed in a sea of free electrons and neutrons. As the neutrons are superfluid their angular momentum is carried by an array of quantized vortices. These vortices can pin to the nuclear lattice and prevent the neutron superfluid from spinning down, allowing it to store angular momentum which can then be released catastrophically, giving rise to a pulsar glitch. A crucial ingredient for this model is the maximum pinning force that the lattice can exert on the vortices, as this allows us to estimate the angular momentum that can be exchanged during a glitch. In this paper we perform, for the first time, a detailed and quantitative calculation of the pinning force per unit length acting on a vortex immersed in the crust and resulting from the mesoscopic vortexlattice interaction. We consider realistic vortex tensions, allow for displacement of the nuclei and average over all possible orientation of the crystal with respect to the vortex. We find that, as expected, the mesoscopic pinning force becomes weaker for longer vortices and is generally much smaller than previous estimates, based on vortices aligned with the crystal. Nevertheless the forces we obtain still have maximum values of order f pin ≈ 10 15 dyn/cm, which would still allow for enough angular momentum to be stored in the crust to explain large Vela glitches, if part of the star is decoupled during the event.

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“…figures 14(b) and 14f ). The two components are loosely coupled because GM friction is weaker than HV friction (|F HV /F GM | ∼ 10 5 ; see Peralta et al (2005Peralta et al ( , 2006b). …”

Section: Effect Of Superfluid Componentmentioning

confidence: 99%

Superfluid spherical Couette flow

et al. 2008

Self Cite

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We solve numerically for the first time the two-fluid Hall-Vinen-BekarevichKhalatnikov (HVBK) equations for an He-II-like superfluid contained in a differentially rotating spherical shell, generalizing previous simulations of viscous spherical Couette flow (SCF) and superfluid Taylor-Couette flow. The simulations are conducted for Reynolds numbers in the range 1 × 10 2 6 Re 6 3 × 10 4 , rotational shear 0.1 6 Ω/Ω 6 0.3, and dimensionless gap widths 0.2 6 δ 6 0.5. The system tends towards a stationary but unsteady state, where the torque oscillates persistently, with amplitude and period determined by δ and Ω/Ω. In axisymmetric superfluid SCF, the number of meridional circulation cells multiplies as Re increases, and their shapes become more complex, especially in the superfluid component, with multiple secondary cells arising for Re > 10 3 . The torque exerted by the normal component is approximately three times greater in a superfluid with anisotropic Hall-Vinen (HV) mutual friction than in a classical viscous fluid or a superfluid with isotropic Gorter-Mellink (GM) mutual friction. HV mutual friction also tends to 'pinch' meridional circulation cells more than GM mutual friction. The boundary condition on the superfluid component, whether no slip or perfect slip, does not affect the large-scale structure of the flow appreciably, but it does alter the cores of the circulation cells, especially at lower Re. As Re increases, and after initial transients die away, the mutual friction force dominates the vortex tension, and the streamlines of the superfluid and normal fluid components increasingly resemble each other. In non-axisymmetric superfluid SCF, three-dimensional vortex structures are classified according to topological invariants. For misaligned spheres, the flow is focal throughout most of its volume, except for thread-like zones where it is strain-dominated near the equator (inviscid component) and poles (viscous component). A wedge-shaped isosurface of vorticity rotates around the equator at roughly the rotation period. For a freely precessing outer sphere, the flow is equally strain-and vorticity-dominated throughout its volume. Unstable focus/contracting points are slightly more common than stable node/saddle/saddle points in the viscous component, but not in the inviscid component. Isosurfaces of positive and negative vorticity form interlocking poloidal ribbons (viscous component) or toroidal tongues (inviscid component) which attach and detach at roughly the rotation period. 222

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Transitions between Turbulent and Laminar Superfluid Vorticity States in the Outer Core of a Neutron Star

Cited by 107 publications

References 119 publications

Spreading of superfluid vorticity clouds in normal-fluid turbulence

Spreading of superfluid vorticity clouds in normal-fluid turbulence

Mesoscopic pinning forces in neutron star crusts

Superfluid spherical Couette flow

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