3.6.3. Recent local origins for the magnetic seeds in galaxies

Many chaotic magnetic fields are ejected by supernovae and by the stellar winds of young stars. These local stellar seed fields are plausibly created at various times within a galaxy by cosmic rays and/or interstellar turbulence (e.g., Poezd et al. 1993). They may be the best to create the real galactic seed fields. The original strengths of such stellar-ejected fields is under debate. Stellar magnetic fields are generated first, then deposited into the interstellar medium by stellar winds and supernovae, yielding a local magnetic field strength 10^-9 Gauss.

The initial amplification of such stellar-ejected magnetic fields is under debate: interstellar turbulences, dynamos, or both. Stellar-ejected fields in turn can be amplified by the random motions of the interstellar turbulence, over a time scale of 10⁷ years and a linear scale of 100 pc. The galactic dynamo would then easily and quickly amplify this seed field to the current values near a few µGauss.