Cosmological magnetic fields from gauge-mediated supersymmetry-breaking models

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