Evolution of cosmic magnetic fields: From the very early Universe, to recombination, to the present

By Robi Banerjee, K. Jedamzik. 2004

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A detailed numerical and analytical examination of the evolution of stochastic magnetic fields between a putative magnetogenesis era at high cosmic temperatures T{approx}100 MeV-100 GeV and the present epoch is presented. The analysis includes all relevant dissipation processes, such as neutrino- and photon-induced fluid viscosities as well as ambipolar and hydrogen diffusion. A simple and intuitive analytical model matching the results of the three-dimensional MHD simulations allows for the prediction of prerecombination and present day magnetic field correlation lengths and energy densities as a function of initial magnetic field energy density, helicity, and spectral index. Our conclusions are multifold. (a) Initial primordial fields with only a small amount of helicity are evolving into maximally helical fields at the present. Furthermore, the simulations show a self-similarity in the evolution of maximally helical fields implying a seemingly acausual amplification of magnetic fields on large scales is observed. (b) There exists a correlation between the strength of the magnetic field B at the peak of its spectrum and the location of the peak, given at the present epoch by B{approx_equal}5x10{sup -12} G(L/kpc), where L is the magnetic field correlation length determined by the initial properties of the magnetic field. (c) Concerning studies ofmore » the generation of cosmic microwave background (CMBR) anisotropies due to primordial magnetic fields of B{approx}10{sup -9} G on > or approx. 10 Mpc scales, such fields are not only impossible to generate in early causal magnetogenesis scenarios but also seemingly ruled out by distortions of the CMBR spectrum due to magnetic field dissipation on smaller scales and the overproduction of cluster-magnetic fields. (d) The most promising detection possibility of CMBR distortions due to primordial magnetic fields may be on much smaller scales at higher multipoles l{approx}10{sup 6} where the signal is predicted to be the strongest. (e) It seems possible that magnetic fields in clusters of galaxies are entirely of primordial origin, without invoking dynamo amplification. Such fields would be of (precollapse) strength 10{sup -12}-10{sup -11} G with correlation lengths in the kpc range and would also exist in voids of galaxies.« less

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/355b2bb3ec7ecbda7610f62128973c2ee091b10a

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Citations in the corpus

Cosmological Magnetic Fields: Their Generation, Evolution and Observation (2013, methodology): “This can be done by replacing the dissipation term by −α̃v, where α̃ ∝ λ−1mfp (see Banerjee and Jedamzik (2004)).”
Small-scale dynamo action during the formation of the first stars and galaxies - I. The ideal MHD limit (2010, background): “By means of the inverse-cascade, the magnetic power of these fields may have been shifted to larger scales in case of non-zero helicity (Brandenburg et al. 1996; Christensson et al. 2001; Banerjee & Jedamzik 2004).”
Can slow roll inflation induce relevant helical magnetic fields (2010, background): “sent in the case discussed above. This has two interesting consequences: ﬁrstly, contrary to non-helical ﬁelds, helical ﬁelds evolve in the cosmic magnetohydrodynamic (MHD) plasma via inverse cascade [31, 32, 33]. This transfers power from small to large scales so that even blue spectra can lead to ”