Origin of Cosmic Magnetic Fields

Biermann, Peter L.; Galea, C.

doi:10.1007/978-94-007-1058-0_21

Cited by 4 publications

(4 citation statements)

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“…These proposals belong to two distinct classes of generating mechanisms, characterized, roughly speaking, by the time when they operate. Astrophysical mechanisms work at the epoch of large-scale structure formation or later, and they can be based on the Biermann battery effect (for a simple and general description of the Biermann battery effect see, e.g., [6]) in the first supernova remnants [7][8][9], or on the Weibel instability [10] in intergalactic plasmas [11]. Mechanisms working in the early universe can, on their part, be classified in mechanisms operating in the very early universe, namely during the inflationary epoch of the universe (for generation mechanisms of magnetic fields at inflation see, e.g., ), and mechanisms operating after inflation ( [58].…”

Section: Introductionmentioning

confidence: 99%

Evolution of primordial magnetic fields in mean-field approximation

Campanelli

2014

Eur. Phys. J. C

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We study the evolution of phase-transitiongenerated cosmic magnetic fields coupled to the primeval cosmic plasma in the turbulent and viscous free-streaming regimes. The evolution laws for the magnetic energy density and the correlation length, both in the helical and the non-helical cases, are found by solving the autoinduction and Navier-Stokes equations in the mean-field approximation. Analytical results are derived in Minkowski spacetime and then extended to the case of a Friedmann universe with zero spatial curvature, both in the radiation-and the matterdominated era. The three possible viscous free-streaming phases are characterized by a drag term in the Navier-Stokes equation which depends on the free-streaming properties of neutrinos, photons, or hydrogen atoms, respectively. In the case of non-helical magnetic fields, the magnetic intensity B and the magnetic correlation length ξ B evolve asymptotically with the temperature, T , asHere, T i , N i , and v i are, respectively, the temperature, the number of magnetic domains per horizon length, and the bulk velocity at the onset of the particular regime. The coefficients κ B , κ ξ , 1 , 2 , 3 , and 4 , depend on the index of the assumed initial power-law magnetic spectrum, p, and on the particular regime, with the order-one constants κ B and κ ξ depending also on the cutoff adopted for the initial magnetic spectrum. In the helical case, the quasi-conservation of the magnetic helicity implies, apart from logarithmic corrections and a factor proportional to the initial fractional helicity, power-like evolution laws equal to those in the non-helical case, but with p equal to zero.

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Section: Introductionmentioning

confidence: 99%

Evolution of primordial magnetic fields in mean-field approximation

Campanelli

2014

Eur. Phys. J. C

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“…There are two classes of models for the seed generation mechanism: astrophysical and cosmological models. In astrophysical models, the seeds are associated with nonlinear structures, and are generated during structure formation through the Biermann battery effect [5], or the Weibel instability [6]. On the other hand, seeds in the cosmological models are produced in the early universe and exist as extragalactic magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

Cosmological magnetic field correlators from blazar induced cascade

Tashiro

Vachaspati

2013

Phys. Rev. D

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“…There are a variety of potential generation mechanisms in both the early and late universe, many of which may well have been in operation, ranging from so-called Biermann batteries (e.g. [5,6]) to fields generated at reionisation [7][8][9][10]. The number of well-motivated magnetogenesis mechanisms would appear to make the existence of magnetic fields across a large range of scales inevitable.…”

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confidence: 99%

“…Since the damping scale is typically rather small, we assume (7) to hold for the power-law fields we consider. In cases where an analytic solution to (5) does not exist the equation can in principle be solved numerically or approximately.…”

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Concerning the statistics of cosmic magnetism

Brown

2010

Preprint

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Magnetic fields appear to be a generic feature of the early universe and are a natural source of secondary CMB non-Gaussianity. In recent years the statistical nature of the stresses of a primordial magnetic field has been well studied. In this paper we confirm and extend these studies at one-and two-point level, and present analytical results for a wide range of power-law spectra. We also consider two non-power law cases of interest: a blue spectrum with an extended damping tail on small scales, which could be generated by the non-linear mixing of density and vorticity; and a red spectrum with a damping tail on large scales. We then briefly consider the CMB impacts that result from such fields. While this paper focuses on the one-and two-point moments, the techniques we employ are designed to ease the analysis of the full bispectra induced by primordial magnetic fields. I. INTRODUCTIONLarge-scale magnetic fields appear to be inevitable. Fields have been observed on galactic and cluster scales and likely exist on supercluster scales [1][2][3][4]. There are a variety of potential generation mechanisms in both the early and late universe, many of which may well have been in operation, ranging from so-called Biermann batteries (e.g. [5,6]) to fields generated at reionisation [7][8][9][10]. The number of well-motivated magnetogenesis mechanisms would appear to make the existence of magnetic fields across a large range of scales inevitable. In particular, plasma processes in the early, pre-recombination universe [11][12][13][14][15][16][17] wherein linear scalar perturbations drive nonlinear vorticity, producing currents in the proton/electron plasmas, would suggest that at least some magnetic fields before recombination are inevitable even if the detailed predictions in the various models differ somewhat. The fields extent in the present universe need not necessarily be primordial; the fields observed on cluster scales can be accounted for in principle by non-linear processes before recombination, by production at reionisation or at recombination [18,19], and it seems probable that each of these processes have contributed. There also many exist potential mechanisms in the extremely early universe, such as magnetogenesis at a phase transition (for example [20][21][22][23][24]).However, all of these fields will have a distinctive, blue power spectrum [25], and the most recent bounds on fields present at or before recombination rather favour a red spectrum [26,27]. It seems reasonable, therefore, to also consider mechanisms that could produce such red fields. To achieve a near-scale invariant spectral index these will necessarily be produced during an inflationary epoch [25], and there is a large variety of potential genesis mechanisms that generate a field from the breaking of the conformal invariance of the electromagnetic field, with [28-33] being a few examples.Constraints on a field produced during the inflationary epoch have naturally focused on the cosmic microwave background (CMB) ([26, 27, 34-36], for example) ...

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Origin of Cosmic Magnetic Fields

Cited by 4 publications

References 51 publications

Evolution of primordial magnetic fields in mean-field approximation

Evolution of primordial magnetic fields in mean-field approximation

Cosmological magnetic field correlators from blazar induced cascade

Concerning the statistics of cosmic magnetism

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