5.2.3. Seeds for magnetic fields in clusters of galaxies
First, a primordial cosmological magnetic field has been proposed, althought very small in strength to comply with its non-detection, and thus it may be unimportant when compared to the turbulent kinetic energy in clusters. It is by no means certain that extremely weak, random, primordial seed magnetic fields < 10-10 Gauss are sufficient to account for observed magnetic fields in clusters of galaxies and in galaxies (e.g., Kim et al. 1996).
A second potential seed field would be coming from the relics of extended double radio sources or radio trails in clusters, being shredded by the turbulent wakes of passing galaxies. However, not all clusters have one or more extended radio doubles or radio trails, and many clusters have none. This seed field may be limited in its application.
A third potential seed field model proposed uses the ejected magnetic field and gas from the interstellar medium of the galaxies in the cluster, which could diffuse out of the galaxies or else be blown out of the galaxies by stellar winds, supernovae, galactic fountains, tidal strippings, etc, at a rate of ~ 1M per galaxy per year (e.g., Goldschmidt & Rephaeli 1993; De Young 1992). This process can be widely distributed and it has the advantage of transfering kinetic energy from the extracting process to the intracluster medium.