The structure of comet Giacobini Zinner's magnetic tail is interpreted in terms of a flow geometry similar to that proposed for the Venus wake. It is suggested that the two-step shape of the magnetic field profile obtained from the ICE measurements across each lobe of the magnetic tail of that comet is due to the different entry of interplanetary magnetic fluxes into that region. The low (~30 &ggr;) intensity outer wings of the magnetic field profile result from magnetic fluxes convected by the mass-loaded shocked solar wind that enters the tail from the polar boundary of the comet's magnetic cavity. The high (~60 &ggr;) intensity inner parts of the lobes result, on the other hand, from the compression that this flow produces on interplanetary magnetic field lines that have slipped past the polar boundary of the cavity after draping around the comet. The latter magnetic fluxes are not convected by the local plasma but forced to accumulate around the central plasma tail that extends behind the comet. ¿ American Geophysical Union 1990