ORCID Profile
0000-0003-2814-6688
Current Organisation
Universidad de Concepcion
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Publisher: American Astronomical Society
Date: 03-12-2014
Publisher: American Physical Society (APS)
Date: 06-08-2015
Publisher: IOP Publishing
Date: 08-02-2013
Publisher: Wiley
Date: 07-2013
Publisher: Cambridge University Press (CUP)
Date: 08-2012
DOI: 10.1017/S1743921313002585
Abstract: The first galaxies form due to gravitational collapse of primordial halos. During this collapse, weak magnetic seed fields get lified exponentially by the small-scale dynamo - a process converting kinetic energy from turbulence into magnetic energy. We use the Kazantsev theory, which describes the small-scale dynamo analytically, to study magnetic field lification for different turbulent velocity correlation functions. For incompressible turbulence (Kolmogorov turbulence), we find that the growth rate is proportional to the square root of the hydrodynamic Reynolds number, Re 1/2 . In the case of highly compressible turbulence (Burgers turbulence) the growth rate increases proportional to Re 1/3 . With a detailed chemical network we are able to follow the chemical evolution and determine the kinetic and magnetic viscosities (due to Ohmic and ambipolar diffusion) during the collapse of the halo. This way, we can calculate the growth rate of the small-scale dynamo quantitatively and predict the evolution of the small-scale magnetic field. As the magnetic energy is transported to larger scales on the local eddy-timescale, we obtain an estimate for the magnetic field on the Jeans scale. Even there, we find that equipartition with the kinetic energy is reached on small timescales. Dynamically relevant field structures can thus be expected already during the formation of the first objects in the Universe.
No related grants have been discovered for Stefano Bovino.