▪ Abstract In most space environments, dust particles are exposed to plasmas and UV radiation and, consequently, carry electrostatic charges. Their motion is influenced by electric and magnetic fields in addition to gravity, drag, and radiation pressure. On the surface of the Moon, in planetary rings, or at comets, for example, electromagnetic forces can shape the spatial and size distribution of micron-sized charged dust particles. The dynamics of small charged dust particles can be surprisingly complex, leading to levitation, rapid transport, energization and ejection, capture, and the formation of new planetary rings. This review briefly discusses the most important processes that determine the charge state of dust particles immersed in plasmas and the resulting dynamics on exposed dusty surfaces and in planetary magnetospheres.

Charged dust dynamics in the solar system

1. Introduction 2. Radial velocities 3. Astrometry 4. Timing 5. Microlensing 6. Transits 7. Imaging 8. Host stars 9. Brown dwarfs and free-floating planets 10. Formation and evolution 11. Interiors and atmospheres 12. The Solar System Appendixes References Index.

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The Exoplanet Handbook

[1] Comets, planetary rings, exposed dusty surfaces, and the zodiacal dust cloud are all examples of environments where dusty plasma effects establish the size and spatial distributions of small grains. Simultaneously, dust often influences the composition, density, and temperature of the plasma surrounding it. The dynamics of charged dust particles can be surprisingly complex and fundamentally different from the well-understood limits of gravitationally dominated motions of neutral particles or the adiabatic motion of electrons and ions in electromagnetic fields that dominate gravity. In this review we focus on observations that are best explained by theories concerning dusty plasma effects at Saturn. In addition to presenting our current models we also discuss our expectations for new discoveries based on existing observations at Jupiter or on purely theoretical considerations. Our intent is to give an up-to-date overview of dusty plasma effects in Saturn's magnetosphere and to draw attention to several outstanding problems that could be resolved by the Cassini mission.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2004RG000151

Dusty plasma effects in Saturn's magnetosphere

Astrophysical dust occurs in many circumstances, like interstellar and circumstellar media, and between and around planets and comets. Typical Solar System applications include planetary rings, asteroid zones, cometary comae and tails, and regions of Earth's lower magnetosphere. Dust grains immersed in ambient plasmas are electrically charged by various processes and interact with electromagnetic fields. Intriguing phenomena observed in the 1980s by Voyager cameras and attributed to charged dust are radial spokes in the B-ring and braids in the F-ring of Saturn. Collective effects become important when the dust intergrain distance is smaller than the plasma Debye length, and start from observations that micron-sized dust grains can have very high negative charges and in proportion even higher masses. Characteristic dust frequencies are considerably smaller than corresponding electron or ion quantities, giving rise to new low-frequency eigenmodes, which could explain some of the low-frequency noise in space and astrophysical plasmas. Repelling electrostatic forces between charged dust grains prevent planetary rings from collapsing to very thin sheets, and oscillations in transverse ring thickness give rise to resonant phenomena, held responsible for gaps in the rings of Jupiter and Saturn. Further features are connected with fluctuating dust charges, which imply highly nontrivial source and/or sink terms in the description, and those in turn lead to new electrostatic and electromagnetic instabilities. Many different papers are reviewed which discuss waves and instabilities in dusty space plasmas, both with fixed and variable dust charges, at the linear level and, at the nonlinear level, involving double layers, solitons, vortices and other waves. These studies are at present far ahead of what observations can corroborate, a situation not likely to change soon due to the paucity of coming solar system missions concerned with planetary or cometary phenomena.

Waves and instabilities in dusty space plasmas

Within 1 AU from Jupiter, the dust detector aboard the Ulysses spacecraft during the flyby on February 8, 1992 recorded periodic bursts of submicron dust particles with durations ranging from several hours to two days and occurring at about monthly intervals. These particles arrived at Ulysses in collimate streams radiating from close to the line-of-sight direction to Jupiter, suggesting a Jovian origin for the periodic bursts. Ulysses also detected a flux of micron-sized dust particles moving in high-velocity retrograde orbits. These grains are identified here as being of interstellar origin.

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M. S. Manner

Papers

Discovery of Jovian dust streams and interstellar grains by the Ulysses spacecraft