We propose a novel mechanism for significantly enhancing the amplitude of
primordial electromagnetic fields during inflation. Similar to existing
proposals, our idea is based on parametric resonance effects due to
conformal-symmetry-breaking coupling of the gauge field and the inflaton. Our
proposed scenario, however, significantly differs from previously studied
models, and avoids their shortcomings. We, particularly, construct a viable
system where the gauge field is exponentially amplified on super-horizon
scales, therefore evading the no-go theorem formulated on the basis of widely
encountered drastic back-reaction of the magnetic field energy on the
inflationary background. We compute the spectrum of the produced magnetic
fields and demonstrate the compatibility with current observational
constraints.
