Dresden 2013 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 21: Astroteilchenphysik und Kosmologie (Theorie)

T 21.8: Vortrag

Mittwoch, 6. März 2013, 18:30–18:45, WIL-B122

Time Evolution of the Large-Scale Tail of Non-Helical Primordial Magnetic Fields — •Andrey Saveliev¹, Karsten Jedamzik², and Günter Sigl¹ — ¹II. Institut für Theoretische Physik, Universität Hamburg, Hamburg, Germany — ²Laboratoire de Physique Theorique et Astroparticules, Université Montpellier II, Montpellier, France

After a general overview on Extragalactic Magnetic Fields (EGMFs) we present a derivation of the time evolution equations for the energy content of nonhelical magnetic fields and the accompanying turbulent flows from first principles of incompressible magnetohydrodynamics in the general framework of homogeneous and isotropic turbulence. This is then applied to the early Universe, i.e., the evolution of primordial magnetic fields which are a reasonable possible seed for EGMFs.

Numerically integrating the equations, we find that most of the energy is concentrated at an integral wavenumber scale k_I where the turbulence turn over time equals the Hubble time. At larger length scales L, i.e., smaller wavenumbers q=2π/L ≪ k_I, independent of the assumed turbulent flow power spectrum, mode-mode coupling tends to develop a small q magnetic field tail with a Batchelor spectrum proportional to the fourth inverse power of L and therefore a scaling for the magnetic field of B ∼ L^−5/2.