In Situ Origin of Large-Scale Galactic Magnetic Fields without Kinetic Helicity?

The origin and sustenance of large-scale galactic magnetic fields has been a long-standing and controversial astrophysical problem. Here an alternative to the "standard" α-Ω mean field dynamo and primordial theories is pursued. The steady supply of supernovae-induced turbulence exponentiates the total field energy, providing a significant seed mean field that can be stretched linearly by shear. The observed microgauss fields would be produced primarily within one vertical diffusion time since it is only during this time that linear stretching can compete with diffusion. This approach does not invoke exponential mean field dynamo growth from the helicity α-effect but does employ turbulent diffusion, which limits the number of large-scale reversals. The approach could be of interest if the helicity effect is suppressed independently of the turbulent diffusion. This is an important but presently unresolved issue.