  We study the pumping of magnetic flux in three-dimensional compressible
magnetoconvection in the context of stellar dynamos. The simulation domain
represents a rectangular section from the lower part of a stellar convection
zone plus the underlying stably stratified layer, with a total depth of up to
five pressure scale heights. Once convection has attained a statistically
stationary state, a magnetic field is introduced. The magnetic field is
subsequently modified by the convective motions, and the resulting pumping
effects are isolated by calculating various coefficients of the expansion of
the electromotive force, uxb, in terms of components of the mean magnetic
field. The dependence of the pumping effects on rotation, latitude and other
parameters is studied. First numerical evidence is found for the existence of
pumping effects in the horizontal directions, unless the rotation axis
coincides with the vertical axis, as is the case on the poles. Evidence is
found that the pumping effects act differently on different components of the
mean magnetic field. Latitudinal pumping is mainly equatorward for toroidal
field, and can be poleward for poloidal field. Longitudinal pumping is mainly
retrograde for the radial field but prograde for the latitudinal field. The
pumping effect in the vertical direction is found to be dominated by the
diamagnetic effect, equivalent to a predominating downward advection with a
maximum speed in the turbulent case of about 10 percent of the rms convective
velocity. Where possible, an attempt is made to identify the physical origin of
the effect. Finally, some consequences of the results for stellar dynamos are
discussed.
