This book observes features in the solar wind interaction with planetary ionospheres (Venus, Mars and comets) that reveal the existence of phenomena similar to those known in fluid dynamics. Those observations are related to concepts in geophysics and astronomy, and are derived from applying the available information to the known interpretation of equivalent problems. Such is the case for predicting the existence of the solar wind as a continuum flow through the solar system, and which leads to vortex structures that are formed in planetary plasma wakes. Those features reveal an outstanding property that could also be produced under similar circumstances in more distant astronomical environments: the interaction of stellar winds with the ionosphere of exoplanets. This may even be related to streaming flows with vortex structures in other astrophysical problems.