954 research outputs found
Cosmological Magnetic Field: a fossil of density perturbations in the early universe
The origin of the substantial magnetic fields that are found in galaxies and
on even larger scales, such as in clusters of galaxies, is yet unclear. If the
second-order couplings between photons and electrons are considered, then
cosmological density fluctuations, which explain the large scale structure of
the universe, can also produce magnetic fields on cosmological scales before
the epoch of recombination. By evaluating the power spectrum of these
cosmological magnetic fields on a range of scales, we show here that magnetic
fields of 10^{-18.1} gauss are generated at a 1 megaparsec scale and can be
even stronger at smaller scales (10^{-14.1} gauss at 10 kiloparsecpc). These
fields are large enough to seed magnetic fields in galaxies and may therefore
have affected primordial star formation in the early universe.Comment: 11 pages, 3 figures, accepted draft for publication in Science.
Edited version and supporting online material are available at:
http://www.sciencemag.org/cgi/content/abstract/311/5762/82
Biermann Mechanism in Primordial Supernova Remnant and Seed Fields
We have studied the generation of magnetic fields by the Biermann mechanism
in the pair-instability supernovae explosions of the first stars. The Biermann
mechanism produces magnetic fields in the shocked region between the bubble and
interstellar medium (ISM), even if magnetic fields are absent initially. We
have performed a series of two-dimensional magnetohydrodynamic simulations with
the Biermann term and estimate the amplitude and total energy of the produced
magnetic fields. We find that magnetic fields with amplitude
G are generated inside the bubble, though the amount of
magnetic fields generated depend on specific values of initial conditions. This
corresponds to magnetic fields of ergs per each supernova
remnant, which is strong enough to be the seed magnetic field for a galactic
and/or interstellar dynamo.Comment: 4pages, 2figures, to appear in the Proc. of the Int. Conference on
"The Origin and Evolution of Cosmic Magnetism", Bologna, 29 August - 2
September 2005, eds. R. Beck, G. Brunetti, L. Feretti and B. Gaensler
(Atronomische Nachrichten, Wiley, 2005
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