Evolution of helical cosmic magnetic fields as predicted by magnetohydrodynamic closure theory

Saveliev, Andrey; Jedamzik, Karsten; Sigl, G.

doi:10.1103/physrevd.87.123001

Cited by 44 publications

(62 citation statements)

References 26 publications

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“…The temperature dependences of B p and λ B of this analytic estimate coincide with the numerical results in Ref. [54]. In the case (ii), the strength and correlation length of magnetic field at T > T TS are given by…”

Section: B Helicity Conservationsupporting

confidence: 86%

Large-scale magnetic fields can explain the baryon asymmetry of the Universe

2016

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Helical hypermagnetic fields in the primordial Universe can produce the observed amount of baryon asymmetry through the chiral anomaly without any ingredients beyond the Standard Model of particle physics. While they generate no B − L asymmetry, the generated baryon asymmetry survives the spharelon washout effect, because the generating process remains active until the electroweak phase transition. Solving the Boltzmann equation numerically and finding an attractor solution, we show that the baryon asymmetry of our Universe can be explained, if the present largescale magnetic fields indicated by the blazar observations have a negative helicity and existed in the early Universe before the electroweak phase transition. We also derive the upper bound on the strength of the helical magnetic field, which is tighter than the CMB constraint, to avoid the overproduction of baryon asymmetry.

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Section: B Helicity Conservationsupporting

confidence: 86%

Large-scale magnetic fields can explain the baryon asymmetry of the Universe

2016

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“…At later times in the system's evolution, this initial anomaly induced helicity, h in will then lead to the realization of maximally helical fields -since magnetic fields with initial fractional helicity become maximally helical due to standard MHD turbulence [75,76]. We thus conclude that the chiral MHD turbulence, when anomaly effects are small compared to the velocity and magnetic field terms, will tend to create maximally helical fields from non-helical fields.…”

Section: Inverse Cascade and The Role Of Helicitymentioning

confidence: 84%

Chiral magnetohydrodynamic turbulence

2017

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In this work the influence of the chiral anomaly effect on the evolution of magnetohydrodynamic turbulence was studied. We argue that before the electroweak symmetry breaking and for temperatures high enough such that the electron mass can be ignored, the description of a charged plasma in general needs to take into account the interplay between turbulence and the anomaly effects. It was demonstrated that this generalization can have important consequences on the evolution of turbulence, leading to the creation of maximally-helical fields from initially non-helical ones. Therefore, chiral effects can strongly support turbulent inverse cascade, and lead to a slower decrease of the magnetic field with time, and also to a faster growth of the correlation length, when compared to the evolution predicted by the standard magnetohydrodynamics description. Using the weak anomaly approximation, and treating the anomaly contributions to magnetic energy and helicity as a small perturbation, we derive the specific solutions for the inverse cascade regime that demonstrate how chiral effects support the inverse cascade.

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“…Lower bounds, B 10 −17 G, have been obtained by several authors using gamma-ray-induced electromagnetic cascades in the intergalactic space [19][20][21][22][23][24][25][26]. These lower bounds are controversial because of the claims [27][28][29][30][31] that the development of the cascade is suppressed by plasma instabilities that arise from interactions with the intergalactic medium. On the other hand, recent direct observations [32] and PIC simulations [33] of cascades suggest that plasma instabilities are not operative and that the orig-inal bounds hold.…”

Section: Introductionmentioning

confidence: 99%

“…Since magnetic helicity affects the dynamical evolution of magnetic fields, an indirect way to measure magnetic helicity is to measure the magnetic field power spectrum and compare it with the evolution seen in magnetohydrodynamical (MHD) simulations [34][35][36]. The magnetic helicity, H, being given by a volume integral is a global quantity, and hence is not directly measurable unless additional assumptions are invoked.…”

Section: Introductionmentioning

confidence: 99%

Probing intergalactic magnetic fields with simulations of electromagnetic cascades

et al. 2016

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We determine the effect of intergalactic magnetic fields on the distribution of high energy gamma rays by performing three-dimensional Monte Carlo simulations of the development of gamma-rayinduced electromagnetic cascades in the magnetized intergalactic medium. We employ the so-called "Large Sphere Observer" method to efficiently simulate blazar gamma ray halos. We study magnetic fields with a Batchelor spectrum and with maximal left-and right-handed helicities. We also consider the case of sources whose jets are tilted with respect to the line of sight. We verify the formation of extended gamma ray halos around the source direction, and observe spiral-like patterns if the magnetic field is helical. We apply the Q-statistics to the simulated halos to extract their spiral nature and also propose an alternative method, the S-statistics. Both methods provide a quantative way to infer the helicity of the intervening magnetic fields from the morphology of individual blazar halos for magnetic field strengths B 10 −15 G and magnetic coherence lengths Lc 100 Mpc. We show that the S-statistics has a better performance than the Q-statistics when assessing magnetic helicity from the simulated halos.

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Evolution of helical cosmic magnetic fields as predicted by magnetohydrodynamic closure theory

Cited by 44 publications

References 26 publications

Large-scale magnetic fields can explain the baryon asymmetry of the Universe

Large-scale magnetic fields can explain the baryon asymmetry of the Universe

Chiral magnetohydrodynamic turbulence

Probing intergalactic magnetic fields with simulations of electromagnetic cascades

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