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The evolution of primordial magnetic fields since their generation
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.ORCID iD: 0000-0002-7304-021X
2016 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 91, no 10, 104008Article in journal (Refereed) Published
Abstract [en]

We study the evolution of primordial magnetic fields in an expanding cosmic plasma. For this purpose we present a comprehensive theoretical model to consider the evolution of MHD turbulence that can be used over a wide range of physical conditions, including cosmological and astrophysical applications. We model different types of decaying cosmic MHD turbulence in the expanding Universe and characterize the large-scale magnetic fields in such a medium. Direct numerical simulations of freely decaying MHD turbulence are performed for different magnetogenesis scenarios: magnetic fields generated during cosmic inflation as well as electroweak and QCD phase transitions in the early Universe. Magnetic fields and fluid motions are strongly coupled due to the high Reynolds number in the early Universe. Hence, we abandon the simple adiabatic dilution model to estimate magnetic field amplitudes in the expanding Universe and include turbulent mixing effects on the large-scale magnetic field evolution. Numerical simulations have been carried out for non-helical and helical magnetic field configurations. The numerical results show the possibility of inverse transfer of energy in magnetically dominated non-helical MHD turbulence. On the other hand, decay properties of helical turbulence depend on whether the turbulent magnetic field is in a weakly or a fully helical state. Our results show that primordial magnetic fields can be considered as a seed for the observed large-scale magnetic fields in galaxies and clusters. Bounds on the magnetic field strength are obtained and are consistent with the upper and lower limits set by observations of extragalactic magnetic fields.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2016. Vol. 91, no 10, 104008
Keyword [en]
cosmic magnetic fields, primordial magnetogenesis, turbulence
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Other Physics Topics
URN: urn:nbn:se:kth:diva-196416DOI: 10.1088/0031-8949/91/10/104008ISI: 000385519200005ScopusID: 2-s2.0-84991780878OAI: diva2:1050237

QC 20161128

Available from: 2016-11-28 Created: 2016-11-14 Last updated: 2016-11-28Bibliographically approved

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Brandenburg, Axel
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