  We consider the corrugated monolayer graphene membrane electromagnetic (from
both valleys) response in terahertz range. We study the generated in irradiated
graphene total current for the first time taking into account both the
synthetic electric fields arising due to the (inevitable) presence in graphene
of inherent out-of-plane nanodeformations and the double-valleys energy
spectrum of Dirac charge particles. Our approach is based on atomistic quantum
mechanics used for the description of valence ${\pi}-{\sigma}$ bonds changes
generated by activating external periodic electric field and also for mechanism
of Dirac electron interaction with this time-dependent perturbation. We
consider the problem in the framework of the model of noninteracting Dirac
electrons. Assuming surface corrugations not to be very rough we obtain for
weak fields the formula for the total current induced in graphene membrane. Our
formula describes the curved current lines in the linear in $E^{ext}(t)$
approximation for the given graphene surface form. We show that the local
direction of current lines is determined by synthetic electric field whose
direction may essentially differ from the one of the external field and depends
on the local curvature of the graphene membrane. We also demonstrate that
valley currents generated by the external field have nonzero elliptic
polarization angles depending on the point (x,y). Valley currents are shown to
rotate in opposite directions in different valleys. The results obtained below
can be applied to the analysis of different devices in terahertz optics and
optoelectronics and the imaging experiments at the Dirac point.
