Motivation

The study of dusty plasmas bridges a number of traditionally separate subjects, for example, celestial mechanics, mechanics of granular materials, and plasma physics. Dust particles, typically micron- and submicron-sized solid objects, immersed in plasmas and UV radiation collect electrostatic charges and respond to electromagnetic forces in addition to all the other forces acting on uncharged grains. Simultaneously, dust can alter its plasma environment by acting as a possible sink and/or source of electrons and ions. Dust particles in plasmas are unusual charge carriers. They are many orders of magnitude heavier than any other plasma particles, and they can have many orders of magnitude larger (negative or positive) time-dependent charges. Dust particles can communicate non-electromagnetic effects, including gravity, neutral gas and plasma drag, and radiation pressure to the plasma electrons and ions. Their presence can influence the collective plasma behavior by altering the traditional plasma wave modes and by triggering new types of waves and instabilities. Dusty plasmas represent the most general form of space, laboratory, and industrial plasmas. Interplanetary space, comets, planetary rings, asteroids, the Moon, and aerosols in the atmosphere, are all examples where electrons, ions, and dust particles coexist.

The observations of the inward transport of interstellar dust and the outflow of near-solar dust provide a unique opportunity to explore dusty plasma processes throughout the heliosphere. The flux, direction, and size distribution of interstellar dust can be used to test our models about the large-scale structure of the heliospheric magnetic fields, and its temporal variability with solar cycle. The measurements of the speed, composition, and size distribution of the recently discovered, solar-wind-entrained, nano-dust particles hold the key to understanding their effects on the dynamics and composition of the solar-wind plasma.

After its fly-by of Jupiter, the dust detector onboard the Ulysses spacecraft detected impacts of particles in the mass range of 10-14 to 10-11 g, predominantly from a direction that was opposite to the expected impact direction of interplanetary dust grains. In addition, the impact velocities exceeded the local solar-system escape velocity (Grün et al., 1993). Subsequent analysis showed that the motion of the interstellar grains through the solar system was approximately parallel to the flow of neutral interstellar hydrogen and helium gas (Fig. 11.1), both traveling at a speed of 26 km/s.