Clouds of dust are often to be found in space between stars and planets. In the interplanetary region dust rings around giant planets are especially striking features. Even fairly small telescopes may be used to observe Saturn's rings. However, dust rings may be extremely faint, making optical observation quite difficult.
Small dust particles are always charged. Dust thus may be regarded as a plasma component but an extremely heavy one. The figures show the penetration of a streaming plasma through a dust cloud got by hybrid code simulation. A supersonic plasma flow is decelerated (left) whereas a subsonic flow is accelerated in the cloud (right). This acceleration is somewhat surprising; however, an analogy can be made to a flow of a liquid in a nozzle: Reduction of the cross section accelerates a subsonic flow. In case of a dense cloud, a complete penetration is impossible and a collisionless shock is excited in front of the cloud as shown in the lower figure.
References
Motschmann, U., K. Sauer, T. Roatsch, Simulation of ion acceleration in a charged dust cloud, Geophys. Res. Lett., 19, 225-228, 1992
Sauer, K., K. Baumgärtel, U. Motschmann, Phobos events as precursors of solar wind dust interaction, Geophys. Res. Lett., 20, 165-168, 1993.