Analysis of the properties of the dayside ionosphere at Venus have shown that two situations are characteristic. One corresponds to the high dynamic pressure of the solar wind, and the other is realized at low dynamic pressure. In both regimes the ionopause manifests itself as a change of the dominant chemical component of plasma rather than the boundary of the magnetized and unmagnetized plasmas (the widely used definition). The nonstationary convection of the magnetized plasma in the Venus dayside ionosphere is analyzed qualitatively. It is argued that the observable large-scale magnetic field in the dayside ionosphere of Venus is the solar wind magnetic field pushed down into the ionosphere during the periods of high solar wind dynamic pressure which evolves under the action of convection and diffusion. The upper boundary of the magnetic belt forms in the vicinity of the upper boundary of the photochemical region. At low dynamic pressures of the solar wind, in a region from approximately 300 km to the ionopause, and upward flux of ionospheric plasma can exist due to motion of plasma can exist due to motion of plasma to the terminator under the day-to-night pressure gradient. With the plasma convection and the results of the study of the Venus ionopause stability taken into account, the destruction of the large-scale ionospheric field is a probable source of flux ropes in the Venus lower ionosphere rather than small-scale ionopause instabilities. ¿ American Geophysical Union 1988