  We consider an ideal parabolic quantum wire in a perpendicular magnetic
field. A simple Gaussian shaped scattering potential well or hill is flashed
softly on and off with its maximum at $t=0$, mimicking a temporary broadening
or narrowing of the wire. By an extension of the Lippmann-Schwinger formalism
to time-dependent scattering potentials we investigate the effects on the
continuous current that is driven through the quantum wire with a vanishingly
small forward bias. The Lippmann-Schwinger approach to the scattering process
enables us to investigate the interplay between geometrical effects and effects
caused by the magnetic field.
