  We study the effect of a magnetic field on Dirac fermions in graphene subject
to a scalar potential oscillating in time. Using the Floquet theory and
resonance approximation, we show that the energy spectrum exhibits extra
subbands resulted from the oscillating potential in addition to quantized
Landau levels. It is found that a current density can be generated in $ x $ and
$ y $-directions that is strongly dependent on the magnetic field and
potential. Our numerical analysis show that the energy spectrum possesses a
symmetry and the current density oscillates with different amplitudes under
various conditions.
