Relativistic charged particles (CR for cosmic-rays) produced by Supernova
explosion of the first generation of massive stars that are responsible for the
re-ionization of the universe escape into the intergalactic medium, carrying an
electric current. Charge imbalance and induction give rise to a return current,
jt, carried by the cold thermal plasma which tends to cancel the CR
current. The electric field, E=ηjt, required to draw the
collisional return current opposes the outflow of low energy cosmic rays and
ohmically heats the cold plasma. Owing to inhomogeneities in the resistivity,
η(T), caused by structure in the temperature, T, of the intergalactic
plasma, the electric field possesses a rotational component which sustains
Faraday's induction. It is found that magnetic field is robustly generated
throughout intergalactic space at rate of 10−17−10−16 Gauss/Gyr, until
the temperature of the intergalactic medium is raised by cosmic reionization.
The magnetic field may seed the subsequent growth of magnetic fields in the
intergalactic environment.Comment: 8 pages, 4 figures, substantially expanded for the sake of a more
detailed presentation of the model. Title slightly simplified. Results
unchanged. Higher resolution version available at
http://www.exp-astro.phys.ethz.ch/miniati/miniatiandbell.pd