Nonhelical turbulence and the inverse transfer of energy: A parameter study

Reppin, Johannes; Banerjee, Rinti

doi:10.1103/physreve.96.053105

Cited by 33 publications

(40 citation statements)

References 39 publications

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“…However, actual equipartition, which one could expect, is not reached and could be related to the fields' intermittent nature over the total volume (Subramanian 1998; Federrath et al 2011). This is also similar to the departure from full equipartition observed in earlier simulations of turbulence with the Pencil-Code (e.g., Reppin & Banerjee 2017).…”

Section: Evolution Of Magnetic and Kinetic Amplitudesupporting

confidence: 88%

Magnetic heating across the cosmological recombination era: results from 3D MHD simulations

Trivedi

Reppin

Chluba

et al. 2018

Monthly Notices of the Royal Astronomical Society

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The origin of cosmic magnetic fields is an unsolved problem and magnetogenesis could have occurred in the early Universe. We study the evolution of such primordial magnetic fields across the cosmological recombination epoch via 3D magnetohydrodynamic numerical simulations. We compute the effective or net heating rate of baryons due to decaying magnetic fields and its dependence on the magnetic field strength and spectral index. In the dragdominated regime (z 1500), prior to recombination, we find no real heating is produced. Our simulations allow us to smoothly trace a new transition regime (600 z 1500), where magnetic energy decays, at first, into the kinetic energy of baryons. A turbulent velocity field is built up until it saturates, as the net heating rate rises from a low value at recombination to its peak towards the end of the transition regime. This is followed by a turbulent decay regime (z 600) where magnetic energy dissipates via turbulent decay of both magnetic and velocity fields while net heating remains appreciable and declines slowly. Both the peak of the net heating rate and the onset of turbulent decay are delayed significantly beyond recombination, by up to 0.5 Myr (until z 600 − 700), for scale-invariant magnetic fields. We provide analytic approximations and present numerical results for a range of field strengths and spectral indices, illustrating the redshift-dependence of dissipation and net heating rates. These can be used to study cosmic microwave background constraints on primordial magnetic fields.

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Section: Evolution Of Magnetic and Kinetic Amplitudesupporting

confidence: 88%

Magnetic heating across the cosmological recombination era: results from 3D MHD simulations

Trivedi

Reppin

Chluba

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…Another problem which may be intimately connected to the flux-tube dynamics is that of the recently reported numerical observation of inverse transfer of magnetic energy in non-helical turbulent systems (Zrake 2014;Brandenburg, Kahniashvili & Tevzadze 2015;Reppin & Banerjee 2017). These results have been met with some surprise, because conventionally in MHD turbulence, the inverse energy transfer associated with the inverse cascade of magnetic helicity is explained by the conservation of non-zero net magnetic helicity (Pouquet 1978;Matthaeus & Lamkin 1986;Christensson, Hindmarsh & Brandenburg 2001).…”

mentioning

confidence: 99%

Multi-scale dynamics of magnetic flux tubes and inverse magnetic energy transfer

2020

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We report on an analytical and numerical study of the dynamics of a three-dimensional array of identical magnetic flux tubes in the reduced-magnetohydrodynamic description of the plasma. We propose that the long-time evolution of this system is dictated by flux-tube mergers, and that such mergers are dynamically constrained by the conservation of the pertinent (ideal) invariants, viz. the magnetic potential and axial fluxes of each tube. We also propose that in the direction perpendicular to the merging plane, flux tubes evolve in a critically balanced fashion. These notions allow us to construct an analytical model for how quantities such as the magnetic energy and the energy-containing scale evolve as functions of time. Of particular importance is the conclusion that, like its two-dimensional counterpart, this system exhibits an inverse transfer of magnetic energy that terminates only at the system scale. We perform direct numerical simulations that confirm these predictions and reveal other interesting aspects of the evolution of the system. We find, for example, that the early time evolution is characterized by a sharp decay of the initial magnetic energy, which we attribute to the ubiquitous formation of current sheets. We also show that a quantitatively similar inverse transfer of magnetic energy is observed when the initial condition is a random, small-scale magnetic seed field.

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“…Here n B and n λ are positive constants, which are determined by the helicity of the magnetic fields and properties of the turbulence [55,56]. Supposing that (i) the equilibration of the magnetic fields and velocity fields 3 and (ii) the coherence length is determined by the eddy scale of the turbulence, λ c ∼ vt ∝ B c t, we have n B ¼ 1 − n λ , which is also seen in the MHD simulations.…”

Section: B Second Stage: V ≠mentioning

confidence: 94%

“…At that stage, the standard MHD studies (without dark magnetic fields) have shown that the magnetic fields evolve according to a scaling law that depends on whether there is an inverse cascade [48][49][50][51], direct cascade [41,48,49,52], or inverse transfer [53][54][55][56]. In any case, as a first approximation, the magnetic fields are described by the comoving field strength B…”

Section: B Second Stage: V ≠mentioning

confidence: 99%

Magnetic field transfer from a hidden sector

Kamada¹,

Tsai²,

Vachaspati³

2018

Phys. Rev. D

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Primordial magnetic fields in the dark sector can be transferred to magnetic fields in the visible sector due to a gauge kinetic mixing term. We show that the transfer occurs when the evolution of magnetic fields is dominated by dissipation due to finite electric conductivity, and does not occur at later times if the magnetic fields evolve according to magnetohydrodynamics scaling laws. The efficiency of the transfer is suppressed by not only the gauge kinetic mixing coupling but also the ratio between the large electric conductivity and the typical momentum of the magnetic fields. We find that the transfer gives nonzero visible magnetic fields today. However, without possible dynamo amplifications, the field transfer is not efficient enough to obtain the intergalactic magnetic fields suggested by the gamma-ray observations, although there are plenty of possibilities for efficient dark magnetogenesis, which are experimentally unconstrained.

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Nonhelical turbulence and the inverse transfer of energy: A parameter study

Cited by 33 publications

References 39 publications

Magnetic heating across the cosmological recombination era: results from 3D MHD simulations

Magnetic heating across the cosmological recombination era: results from 3D MHD simulations

Multi-scale dynamics of magnetic flux tubes and inverse magnetic energy transfer

Magnetic field transfer from a hidden sector

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