Anomalous global strings and primordial magnetic fields - art. no. 081301

We propose a new mechanism for the generation of primordial magnetic fields , making use of the magnetic fields which are induced by anomalous global s trings, such as pion and axion strings, which couple to electromagnetism vi a Wess-Zumino type interactions. We calculate the magnitude and coherence l ength of these fields. They are seen to depend on the string dynamics. With optimistic assumptions, both the magnitude and coherence scale of the indu ced magnetic fields can be large enough to explain the seed magnetic fields of greater than 10(-23) G necessary to produce the observed galactic magne tic fields via the galactic dynamo mechanism. [S0556-2821(99)50306-8].