The collisionless flow of unmagnetized plasmas around bodies

The ion density in the wake of extended bodies in collisionless flows of unmagnetized plasmas is qualitatively investigated. Both the deflexion of the ions in a surface potential field, and the collective response of the ambient plasma are incorporated in a model which reveals the connexion between the wakes of extended bodies and those of point charges. The differences between the wake features of small and large bodies in strongly non-isothermal plasmas (Te » Ti) are related to the excitation of different types of waves. In isothermal plasmas no sharp wake features can be expected, because the appropriate waves are heavily damped, and other features are smoothed by the thermal motion of the ions.