  The production of the hypermagnetic gyrotropy is investigated under the
assumption that the gauge coupling smoothly evolves during a quasi-de Sitter
phase and then flattens out in the radiation epoch by always remaining
perturbative. In the plane defined by the strength of the anomalous
interactions and by the rate of evolution of the gauge coupling the actual
weight of the pseudoscalar interactions turns out to be always rather modest if
major deviations from the homogeneity are to be avoided during the inflationary
phase. Even if the gauge power spectra are related by duality only in the
absence of anomalous contributions, an approximate duality symmetry constrains
the late-time form of the hypermagnetic power spectra. Since the hypermagnetic
gyrotropy associated with the modes reentering prior to the phase transition
must be released into fermions later on, the portions of the parameter space
where the obtained baryon asymmetry is close to the observed value are the most
relevant for the present ends. For the same range of parameters the magnetic
power spectra associated with the modes reentering after symmetry breaking may
even be of the order of a few hundredths of a nG over typical length scales
comparable with the Mpc prior to the collapse of the protogalaxy.
