  Nondipole effects are ubiquitous and crucial in light-matter interaction.
However, they are too weak to be directly observed. In strong-field physics,
motion of electrons is mainly confined in transverse plane of light fields,
which suppresses the significance of nondipole effects. Here, we present a
theoretical study on enhancing and controlling the nondipole effect by using
the synthesized two perpendicularly propagating laser fields. We calculate the
three-dimensional photoelectron momentum distributions of strong-field
tunneling ionization of hydrogen atoms using the classical trajectory Monte
Carlo model and show that the nondipole effects are noticeably enhanced in such
laser fields due to their remarkable influences on the sub-cycle photoelectron
dynamics. In particular, we reveal that the magnitudes of the magnetic and
electric components of nondipole effects can be separately controlled by
modulating the ellipticity and amplitude of driving laser fields. This novel
scenario holds promising applications for future studies with ultrafast
structured light fields.
