Axial dipolar dynamo action in the Taylor-Green vortex

Krstulovic, Giorgio; Thorner, Gentien; Vest, Julien-Piera; Fauve, S.; Brachet, Marc

doi:10.1103/physreve.84.066318

Cited by 41 publications

(23 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In principle, above a critical Reynolds number R C M , a dynamo mechanism sets in whereby sufficient magnetic excitation is produced at all scales. For the Taylor-Green flow defined below it was shown in reference [7] that R C M depends very strongly on the imposed symmetries. In addition, when imposing all symmetries at all times, it was shown in reference [8] that R C M is very high (of the order of 1000).…”

Section: The Equations and The Numerical Set-upmentioning

confidence: 99%

Forced magnetohydrodynamic turbulence in three dimensions using Taylor-Green symmetries

Krstulovic

Brachet²,

Pouquet

2014

Phys. Rev. E

View full text Add to dashboard Cite

We examine the scaling laws of magnetohydrodynamic (MHD) turbulence for three different types of forcing functions and imposing at all times the fourfold symmetries of the Taylor-Green (TG) vortex generalized to MHD; no uniform magnetic field is present and the magnetic Prandtl number is equal to unity. We also include pumping in the induction equation, and we take the three configurations studied in the decaying case in Lee et al. [Phys. Rev. E 81, 016318 (2010)]. To that effect, we employ direct numerical simulations up to an equivalent resolution of 20483 grid points. We find that, similarly to the case when the forcing is absent, different spectral indices for the total energy spectrum emerge, corresponding to either a Kolmogorov law, an Iroshnikov-Kraichnan law that arises from the interactions of turbulent eddies and Alfvén waves, or to weak turbulence when the large-scale magnetic field is strong. We also examine the inertial range dynamics in terms of the ratios of kinetic to magnetic energy, and of the turnover time to the Alfvén time, and analyze the temporal variations of these quasiequilibria.

show abstract

Section: The Equations and The Numerical Set-upmentioning

confidence: 99%

Forced magnetohydrodynamic turbulence in three dimensions using Taylor-Green symmetries

Krstulovic

Brachet²,

Pouquet

2014

Phys. Rev. E

View full text Add to dashboard Cite

show abstract

“…One possibility is that the entire dynamo process is a finite amplitude rather than a linear instability (as encountered also in other contexts, e.g., Refs. [21][22][23]). That is, an infinitesimally small seed field would yield neither turbulence nor a dynamo, but some sufficiently strong initial field could yield a configuration that permanently maintains both the turbulence and an associated magnetic field.…”

mentioning

confidence: 99%

Dynamo Action in a Quasi-Keplerian Taylor-Couette Flow

Guseva¹,

Hollerbach²,

Willis³

et al. 2017

Phys. Rev. Lett.

View full text Add to dashboard Cite

We numerically compute the flow of an electrically conducting fluid in a Taylor-Couette geometry where the rotation rates of the inner and outer cylinders satisfy Ω o =Ω i ¼ ðr o =r i Þ −3=2 . In this quasi-Keplerian regime, a nonmagnetic system would be Rayleigh stable for all Reynolds numbers Re, and the resulting purely azimuthal flow incapable of kinematic dynamo action for all magnetic Reynolds numbers Rm. For Re ¼ 10 4 and Rm ¼ 10 5 , we demonstrate the existence of a finite-amplitude dynamo, whereby a suitable initial condition yields mutually sustaining turbulence and magnetic fields, even though neither could exist without the other. This dynamo solution results in significantly increased outward angular momentum transport, with the bulk of the transport being by Maxwell rather than Reynolds stresses.

show abstract

“…Then, for λ > 0, as the hydrodynamic mode becomes more and more linearly unstable, the linear dynamo threshold drops faster than the subcritical threshold, which results in recovering a supercritical bifurcation at large λ (see upper inset in Fig.9). This model shares several similarities with the equations derived in [35], who recently used a dynamical system to show that a competition between an hydrodynamic instability and a growing magnetic mode can lead to a subcritical dynamo. Note however that the 1:2 resonance underlying the present approach directly constrain the symmetry of the modes that can be involved in the bifurcation, and the quadratic order of the coupling terms provides a direct identification to the original MHD equations from which the model is derived.…”

Section: Low-dimensional Model For the Subcritical Dynamo Bifurcationmentioning

confidence: 52%

Dynamo generated by the centrifugal instability

Marcotte

Gissinger²

2016

Phys. Rev. Fluids

View full text Add to dashboard Cite

We present a new scenario for magnetic field amplification where an electrically conducting fluid is confined in a differentially rotating, spherical shell with thin aspect-ratio. When the angular momentum sufficiently decreases outwards, an hydrodynamic instability develops in the equatorial region, characterised by pairs of counter-rotating toroidal vortices similar to those observed in cylindrical Couette flow. These spherical TaylorCouette vortices generate a subcritical dynamo magnetic field dominated by non-axisymmetric components. We show that the critical magnetic Reynolds number seems to reach a constant value at large Reynolds number and that the global rotation can strongly decrease the dynamo onset. Our numerical results are understood within the framework of a simple dynamical system, and we propose a low-dimensional model for subcritical dynamo bifurcations. Implications for both laboratory dynamos and astrophysical magnetic fields are finally discussed.

show abstract

Axial dipolar dynamo action in the Taylor-Green vortex

Cited by 41 publications

References 34 publications

Forced magnetohydrodynamic turbulence in three dimensions using Taylor-Green symmetries

Forced magnetohydrodynamic turbulence in three dimensions using Taylor-Green symmetries

Dynamo Action in a Quasi-Keplerian Taylor-Couette Flow

Dynamo generated by the centrifugal instability

Contact Info

Product

Resources

About