Inflation-produced magnetic fields in RnF2 and IF2 models

We reanalyze the production of seed magnetic fields during inflation in (R/m(2))(F mu nu F mu nu)-F-n and IF mu nu F mu nu models, where n is a positive integer, R the Ricci scalar, m a mass parameter, and I proportional to eta(alpha) a power-law function of the conformal time eta, with alpha a positive real number. If m is the electron mass, the produced fields are uninterestingly small for all n. Taking m as a free parameter, we find that, for n >= 2, the produced magnetic fields can be sufficiently strong in order to seed the dynamo mechanism and then to explain galactic magnetism. For alpha greater than or similar to 2, there is always a window in the parameters defining inflation such that the generated magnetic fields are astrophysically interesting. Moreover, if inflation is (almost) de Sitter and the produced fields almost scale invariant (alpha similar or equal to 4), their intensity can be strong enough to directly explain the presence of microgauss galactic magnetic fields.