  Recent observations revealed that small magnetic elements abundant at the
solar surface move poleward with a velocity which seems to be lower than the
plasma velocity $U_{\theta}$. Guerrero et al. (2011) explained this discrepancy
as a consequence of diffusive spreading of the magnetic elements due to a
positive radial gradient of $|U_{\theta}|$. As the gradient's sign (inferred by
local helioseismology) is still unclear, cases with a negative gradient are
studied in this paper. Under this condition, the velocity of the magnetic
tracers turns out to be larger than the plasma velocity, in disagreement with
the observations. Alternative mechanisms for explaining them independently are
proposed. For the turbulent magnetic pumping it is shown that it has to be
unrealistically strong to reconcile the model with the observations.
