Decaying homogeneous turbulence under strong density stratification at low-Prandtl number

Iida, Oaki; Tsuzuki, Naofumi; Nagano, Yasutaka

doi:10.1007/s00162-009-0101-1

Cited by 8 publications

(8 citation statements)

References 38 publications

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“…Even for Fr −1 10 2 , the turbulence is not quenched, if Re is sufficiently large. Turbulence persists for Re Fr −2 or equivalently R 2 (∆Ω) 3 νN 2 , where ν is the kinematic viscosity (Iida et al 2009;Lasky et al 2013). Neutron stars lie near the boundary defined by the above condition in the Fr −1 -Re plane.…”

Section: Superfluid Turbulencementioning

confidence: 93%

Magnetic Field Generation in Stars

Ferrario

Melatos

Zrake

2016

The Strongest Magnetic Fields in the Universe

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Enormous progress has been made on observing stellar magnetism in stars from the main sequence (particularly thanks to the MiMeS, MAGORI and BOB surveys) through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence, in the generation and stability of neutron star fields.Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Coherent searches for the Crab pulsar with the Laser Interferometer Gravitational Wave Observatory (LIGO) have already constrained its gravitational wave luminosity to be 2% of the observed spin-down luminosity, thus placing a limit of 10 16 G on the internal field. Indirect spin-down limits inferred from recycled pulsars also yield interesting gravitational-wave-related constraints. Thus we may be at the dawn of a new era of exciting discoveries in compact star magnetism driven by the opening of a new, non-electromagnetic observational window.We also review recent advances in the theory and computation of magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo theory. These advances offer insight into the action of stellar dynamos as well as processes which control the diffusive magnetic flux transport in stars.

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Section: Superfluid Turbulencementioning

confidence: 93%

Magnetic Field Generation in Stars

Ferrario

Melatos

Zrake

2016

The Strongest Magnetic Fields in the Universe

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show abstract

“…Even for Fr −1 10 2 , the turbulence is not quenched, if Re is sufficiently large. Turbulence persists for Re Fr −2 or equivalently R 2 (ΔΩ) 3 νN 2 , where ν is the kinematic viscosity (Iida et al 2009;Lasky et al 2013). Neutron stars lie near the boundary defined by the above condition in the Fr −1 -Re plane.…”

Section: Superfluid Turbulencementioning

confidence: 96%

Magnetic Field Generation in Stars

2015

View full text Add to dashboard Cite

Enormous progress has been made on observing stellar magnetism in stars from the main sequence through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence,in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Thus we maybe at the dawn of a new era of exciting discoveries in compact star magnetism driven by the opening of a new, non-electromagnetic observational window. We also review recent advances in the theory and computation of magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo theory. These advances offer insight into the action of stellar dynamos as well as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field generation in stars to appear in Space Science Reviews, Springe

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“…spherical shells) only when the activity parameter Ro 3 S −1 E −1 drops below ≈ 7, which condition is avoided for Ro 10 −2 , i.e. throughout much of Figure 1 [see Iida et al (2009) and§2 in Melatos &Peralta (2010)]. Stochastic gravitational radiation from hydrodynamic turbulence imposes a fundamental noise floor on gravitational-wave observations of fossil rotators with Ro 1 even with the current generation of long-baseline interferometers (Melatos & Peralta 2010).…”

Section: Observational Signaturesmentioning

confidence: 99%

Fast Fossil Rotation of Neutron Star Cores

Melatos

2012

ApJ

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It is argued that the superfluid core of a neutron star super-rotates relative to the crust, because stratification prevents the core from responding to the electromagnetic braking torque, until the relevant dissipative (viscous or Eddington-Sweet) time-scale, which can exceed ∼ 10 3 yr and is much longer than the Ekman timescale, has elapsed. Hence, in some young pulsars, the rotation of the core today is a fossil record of its rotation at birth, provided that magnetic crust-core coupling is inhibited, e.g. by buoyancy, field-line topology, or the presence of uncondensed neutral components in the superfluid. Persistent core super-rotation alters our picture of neutron stars in several ways, allowing for magnetic field generation by ongoing dynamo action and enhanced gravitational wave emission from hydrodynamic instabilites.1 In this paper, we restrict attention to the spin-down problem relevant to an electromagnetically braking neutron star.

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Decaying homogeneous turbulence under strong density stratification at low-Prandtl number

Cited by 8 publications

References 38 publications

Magnetic Field Generation in Stars

Magnetic Field Generation in Stars

Magnetic Field Generation in Stars

Fast Fossil Rotation of Neutron Star Cores

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