Galactic Magnetic Fields from Superconducting Strings

Abstract

We use a simple analytic model for the evolution of currents in superconducting strings to estimate the strength of the `seed' magnetic fields generated by these strings. This model is an extension of the evolution model of Martins and Shellard depending on a parameter $f$ which characterizes the importance of equilibration process in the evolution of the currents. For GUT-scale strings, we find that a viable seed magnetic field for the galactic dynamo can be generated if equilibration is weak. On the other hand, electroweak-scale strings originate magnetic fields that are smaller than required.