  Recent Sunrise/IMaX observations have revealed the existence of supersonic
magnetic flows. Our aim is to determine the origin of such flows by using
realistic MHD simulations. We simulate cancellation and emergence of magnetic
flux through the solar photosphere. Our first numerical experiment starts with
magnetic field of both polarities. To simulate emergence into a region with
pre-existing field, we introduce a large-scale horizontally uniform sheet of
horizontal field. We follow the subsequent evolution, creating synthetic
polarimetric observations, including known instrumental effects of the
Sunrise/IMaX and Hinode/SP instruments. We compare the simulated and observed
spectropolarimetric signals. Strongly blue- and redshifted Stokes V signals are
produced in locations where strong line-of-sight velocities coincide with the
strong line-of-sight component of magnetic field. The size and strength of
simulated events is smaller than observed and they are mostly associated with
downflows, contrary to observations. In a few cases where they appear above a
granule, single blue lobed Stokes V are produced due to strong gradients in
magnetic field and velocity. No change of magnetic field sign is detected along
the line of sight in these instances. More high-speed magnetized flows occur in
the case where emergence is simulated than in the case where no horizontal
field was added. The simulations indicate that the observed events result from
magnetic flux emergence, where reconnection may take place but does not seem to
be necessary.
