The joule dissipation inside flux ropes in Venus' ionosphere is so great that they must be formed near, and maintained at, the place where they are observed. Thus ropes are not formed by a Kelvin--Helmholtz instability of the ionopause. The hypothesis that ropes may be formed by the dynamo action of internal gravity waves in Venus' thermosphere (Luhmann and Elphic, 1985; Cole, 1993) is strengthened by discussion of a magnetic evolution equation which includes neutral air motion. However, the dynamo process would work only at altitudes at which &ngr;in≥&ohgr;i. At altitudes or parts of a rope where &ngr;n≪&ohgr;i, the process does not work. A solar wind dynamo is therefore examined to account for the ropes. Thereby a major new heat source for ions of the Venus ionosphere associated with the ropes is uncovered.