Origin of primordial magnetic fields

Abstract

Magnetic fields of intensities similar to those in our galaxy are also observed in high redshift galaxies, where a mean field dynamo would not have had time to produce them. Therefore, a primordial origin is indicated. It has been suggested that magnetic fields were created at various primordial eras: during inflation, the electroweak phase transition, the quark-hadron phase transition (QHPT), during the formation of the first objects, and during reionization. We suggest here that the large scale fields ∼ µG, observed in galaxies at both high and low redshifts by Faraday Rotation Measurements (FRMs), have their origin in the electromagnetic fluctuations that naturally occurred in the dense hot plasma that existed just after the QHPT. We evolve the predicted fields to the present time. The size of the region containing a coherent magnetic field increased due to the fusion of smaller regions. Magnetic fields (MFs) ∼ 10µG over a comoving ∼ 1 pc region are predicted at redshift z ∼ 10. These fields are orders of magnitude greater than those predicted in previous scenarios for creating primordial magnetic fields. Line-of-sight average magnetic fields (MFs) ∼ 10 −2 µG, valid for FRMs, are obtained over a 1 Mpc comoving region at the redshift z ∼ 10. In the collapse to a galaxy (comoving size ∼ 30 kpc) at z ∼ 10, the fields are amplified to ∼ 10µG. This indicates that the MFs created immediately after the QHPT (10 −4 s), predicted by the Fluctuation-Dissipation Theorem, could be the origin of the ∼ µG fields observed by FRMs in galaxies at both high and low redshifts. Our predicted MFs are shown to be consistent with present observations. We discuss the possibility that the predicted MFs could cause non-negligible deflections of ultra-high energy cosmic rays and help create the observed isotropic distribution of their incoming directions. We also discuss the importance of the volume average magnetic field predicted by our model in producing the first stars and in reionizing the Universe.

News and Views: Challenges of Relativistic Astrophysics

“…One of the most interesting suggestions for the origin of cosmic magnetic fields, which does not rely on any ad hoc assumption, is the natural fluctuations of the dense hot primordial plasma, as predicted by the Fluctuation Dissipation Theorem. It was shown that fluctuations produced in the high redshift plasma, after the primordial quark-hadron transition, could produce the present observed cosmic magnetic fields (7,8). Many other scenarios have previously been suggested.…”

Origin of magnetic fields in galaxies

“…The origin of large-scale cosmic magnetic fields in galaxies and protogalaxies remains a challenging problem in astrophysics [1][2][3][4]. There have been many attempts to explain the origin of cosmic magnetic fields.…”

Sobre o problema da falta de galáxias satélites

“…de Souza & Opher (2008 showed that the application of the Fluctuation Dissipation Theorem immediately after the quark-hadron transition lead to the pro-duction of magnetic fields with average intensity B = 9 µG (0.1 pc/L) 3/2 for a region of size L.…”

“…A common outcome of primordial magnetic field models is the case where each cell contains a dipole field, which leads to p = 3/2 (Hindmarsh & Everett, 1998;de Souza & Opher, 2008.…”

“…For a random magnetic field, the magnetic pressure in a region of comoving size L greater than the comoving size of a magnetic cell, L 0 , is given by (Hindmarsh & Everett, 1998) p = B 2 rms 8π (7.5) with the following expression for the rms average of the field (Grasso & Rubinstein, 2001;de Souza & Opher, 2008)…”