Self‐generated Magnetic Fields in Galactic Cooling Flows

Interstellar magnetic fields in elliptical galaxies are assumed to have theirorigin in stellar fields that accompany normal mass loss from an evolvingpopulation of old stars. The seed fields are amplified by interstellarturbulence driven by stellar mass loss and supernova events. These disorderedfields are further amplified by time-dependent compression in the inward movinggalactic cooling flow and are expected to dominate near the galactic core.Under favorable circumstances, fields similar in strength to those observed $B\sim 1-10~(r/10~kpc)^{-1.2}\mu$G can be generated solely from these naturalgalactic processes. In general the interstellar field throughout ellipticalgalaxies is determined by the outermost regions in the interstellar gas wherethe turbulent dynamo process can occur. Because of the long hydrodynamic flowtimes in galactic cooling flows, currently observed magnetic fields may resultfrom periods of intense turbulent field amplification that occurred in theouter galaxy in the distant past. Particularly strong fields in ellipticals mayresult from ancient galactic mergers or shear turbulence introduced at theboundary between the interstellar gas and ambient cluster gas.Comment: 21 pages in AASTEX LaTeX with 2 figures; accepted by Astrophysical Journa