  We simulate the magnetic feature tracking (MFT) speed using
advective-diffusive transport models in both one and two dimensions. By
depositing magnetic bipolar regions at different latitudes at the Sun's surface
and following their evolution for a prescribed meridional circulation and
magnetic diffusivity profiles, we derive the MFT speed as a function of
latitude. We find that in a one dimensional surface-transport model the
simulated MFT speed at the surface is always the same as the meridional
flow-speed used as input to the model, but is different in a two-dimensional
transport model in the meridional (r,theta) plane. The difference depends on
the value of the magnetic diffusivity and on the radial gradient of the
latitudinal velocity. We have confirmed our results with two different codes in
spherical and Cartesian coordinates.
