  We consider helical coupling to electromagnetism and present a simple
scenario of evolution of the coupling function leading to a viable inflationary
magnetogenesis without the problem of back-reaction. In this scenario, helical
magnetic fields of strength of order up to $10^{- 7}\,\text{G}$, when
extrapolated to the current epoch, can be generated in a narrow spectral band
centered at any reasonable wavenumber by adjusting the model parameters. We
discuss implications of this model for baryogenesis, which impose additional
constraints on the strength and correlation length of magnetic field.
