Interpreting Superfluid Spin Up Through the Response of the Container

Eysden, C. A. van; Melatos, A.

doi:10.1007/s10909-011-0444-z

Cited by 8 publications

(2 citation statements)

References 103 publications

(204 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The power spectrum P (k) extends as a power law from the outer (stirring) scale k s = 2π/R to the inner (dissipation) scale k d = (8ε/27ν 3 ) 1/4 . The kinematic viscosity ν in a superfluid arises from a combination of particle collisions moderated by transverse Landau damping (Shternin & Yakovlev 2008) and a Kelvin wave cascade on vortex lines; the latter channel is especially prominent under turbulent conditions in helium (Eltsov et al 2007;Walmsley et al 2007;van Eysden & Melatos 2012). The value of ν inside a neutron star is still poorly known, but the theory in this paper is insensitive to it with respect to timing noise observables.…”

Section: Angular Momentum Fluctuationsmentioning

confidence: 90%

Pulsar timing noise from superfluid turbulence

Melatos¹,

Link²

2013

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Shear-driven turbulence in the superfluid interior of a neutron star exerts a fluctuating torque on the rigid crust, causing the rotational phase to walk randomly. The phase fluctuation spectrum is calculated analytically for incompressible Kolmogorov turbulence and is found to be red; the half-power point is set by the observed spin-down rate, the crust-superfluid lag, and the dynamical response time of the superfluid. Preliminary limits are placed on the latter quantities using selected time-and frequency-domain data. It is found that measurements of the normalization and slope of the power spectrum are reproduced for reasonable choices of the turbulence parameters. The results point preferentially to the neutron star interior containing a turbulent superfluid rather than a turbulent Navier-Stokes fluid. The implications for gravitational wave detection by pulsar timing arrays are discussed briefly.

show abstract

Section: Angular Momentum Fluctuationsmentioning

confidence: 90%

Pulsar timing noise from superfluid turbulence

Melatos¹,

Link²

2013

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…𝑛 the crust to the superfluid core (e.g. Smith 1999;Antonopoulou et al 2018;Pizzochero et al 2020;Montoli et al 2020), unpinning and re-pinning of vortices between crustal pinning sites due to thermal fluctuations (the 'vortex creep' model; Alpar et al 1984aAlpar et al ,b, 1993Alpar & Baykal 2006;Akbal et al 2017) and turbulence within an array of vortices pinned in the superfluid (Melatos & Peralta 2007;van Eysden & Melatos 2012;Melatos & Link 2014;Haskell et al 2020).…”

Section: Psrjmentioning

confidence: 99%

The impact of glitches on young pulsar rotational evolution

Lower,

Johnston,

Dunn

et al. 2021

Preprint

View full text Add to dashboard Cite

We report on a timing programme of 74 young pulsars that have been observed by the Parkes 64-m radio telescope over the past decade. Using modern Bayesian timing techniques, we have measured the properties of 124 glitches in 52 of these pulsars, of which 74 are new. We demonstrate that the glitch sample is complete to fractional increases in spin-frequency greater than Δ𝜈 90%𝑔 /𝜈 ≈ 9.3 × 10 −9 . We measure values of the braking index, 𝑛, in 33 pulsars. In most of these pulsars, their rotational evolution is dominated by episodes of spin-down with 𝑛 > 10, punctuated by step changes in the spin-down rate at the time of a large glitch. The step changes are such that, averaged over the glitches, the long-term 𝑛 is small. We find a near one-to-one relationship between the inter-glitch value of 𝑛 and the change in spin-down of the previous glitch divided by the inter-glitch time interval. We discuss the results in the context of a range of physical models.

show abstract

Spin-up of a two-component superfluid: analytic theory in arbitrary geometry

Eysden

Melatos

2013

J. Fluid Mech.

View full text Add to dashboard Cite

The impulsive spin-up of a two-component superfluid and its container is solved analytically for the first time in arbitrary geometry, generalizing the extensively studied case of single-fluid spin-up. The superfluid is modelled by the Hall–Vinen–Bekarevich–Khalatnikov (HVBK) two-fluid equations, neglecting non-hydrodynamic processes like vortex tension and pinning, which are weak in certain applications (e.g. neutron stars) and confined to boundary layers in the inviscid HVBK component in other applications (e.g. helium II spin-up in smooth-walled containers). Both components of the flow are found to be columnar. The spin-up time depends on the geometry, mutual friction coefficients, $B$, ${B}^{\prime } $, the Ekman number $E$, and the superfluid density fraction ${\rho }_{n} $. For $B\sim O(1)$, the inviscid component undergoes Ekman pumping due to strong coupling to the viscous component, and the azimuthal velocities are ‘locked together’ during the spin-up. For $B\lesssim {E}^{1/ 2} $, there is no Ekman pumping in the inviscid component and the inviscid azimuthal velocity spins up via mutual friction on a combination of the mutual friction and Ekman time scales. The spin-up process is studied in spheres, cylinders (with co- and counter-rotating lids), and cones, and occurs faster in spheres and cones. Ekman pumping is (anti-) clockwise adjacent to the (lower-) upper-right boundary, and mirrored about the rotation axis. The solution obtained by Reisenegger (J. Low Temp. Phys., vol. 92, 1993, p. 77) between slowly accelerating parallel plates is recovered in the associated limit. The hydrodynamic torque on the container decays dual-exponentially with time in a cylinder but not in a sphere or cone, where it is a superposition of exponentials whose time scales vary with latitude. The torque is a good diagnostic of the flow; e.g. it is steepest initially in a sphere with strong mutual friction.

show abstract

Interpreting Superfluid Spin Up Through the Response of the Container

Cited by 8 publications

References 103 publications

Pulsar timing noise from superfluid turbulence

Pulsar timing noise from superfluid turbulence

The impact of glitches on young pulsar rotational evolution

Spin-up of a two-component superfluid: analytic theory in arbitrary geometry

Contact Info

Product

Resources

About