  In the Ratra scenario of inflationary magnetogenesis, the kinematic coupling
between the photon and the inflaton undergoes a nonanalytical jump at the end
of inflation. Using smooth interpolating analytical forms of the coupling
function, we show that such unphysical jump does not invalidate the main
prediction of the model, which still represents a viable mechanism for
explaining cosmic magnetization. Nevertheless, there is a spurious result
associated with the nonanaliticity of the coupling, to wit, the prediction that
the spectrum of created photons has a power-law decay in the ultraviolet
regime. This issue is discussed using both semiclassical approximation and
smooth coupling functions.
