Cosmological magnetic fields from gauge-mediated supersymmetry-breaking models

We study the generation of primordial magnetic fields, coherent over cosmologically interesting scales, by gravitational creation of charged scalar particles during the reheating period. We show that magnetic fields consistent with those detected by observation may be obtained if the particle mean life tau(s) is in the range 10(-14) s less than or similar to tau(s) less than or similar to 10(-7) s. We apply this mechanism to minimal gauge-mediated supersymmetry-breaking models, in the case in which the lightest stau <(tau)over tilde>(1) is the next-to-lightest supersymmetric particle. We show that, for a large range of phenomenologically acceptable values of the supersymmetry-breaking scale root F, the generated primordial magnetic field can be strong enough to seed the galactic dynamo. (C) 2000 Elsevier Science B.V. All rights reserved.