  Magnetic flux tubes reaching from the solar convective zone into the
chromosphere have to pass through the relatively cool, and therefore non-ideal
(i.e. resistive) photospheric region enclosed between the highly ideal
sub-photospheric and chromospheric plasma. It is shown that stationary MHD
equilibria of magnetic flux tubes which pass through this region require an
inflow of photospheric material into the flux tube and a deviation from
iso-rotation along the tube axis. This means that there is a difference in
angular velocity of the plasma flow inside the tube below and above the
non-ideal region. Both effects increase with decreasing cross section of the
tube. Although for characteristic parameters of thick flux tubes the effect is
negligible, a scaling law indicates its importance for small-scale structures.
The relevance of this "inflow effect" for the expansion of flux tubes above the
photosphere is discussed.
