The processes that lead to charging of dust grains in a plasma are briefly reviewed. Whereas for single grains the results have been long known, the reduction of the average charge on a grain by 'Debye screening' has only recently been discovered. This reduction can be important in the Jovian ring and in the rings of Uranus. The emerging field of gravitoelectrodynamics which deals with the motion of charged grains in a planetary magnetosphere is then reviewed. Important mechanisms for distributing grains in radial distance are due to stochastic fluctuations of the grain charge and a systematic variation due to motion through plasma gradients. The electrostatic levitation model for the formation of spokes is discussed, and it is shown that the radial transport of dust contained in the spokes may be responsible for the rich radial structure in Saturn's rings. Finally, collective effects in dusty plasmas are discussed which affect various waves, such as density waves in planetary rings and low-frequency plasma waves. The possibility of charged grains forming a Coulomb lattice is briefly described.

Dusty plasmas 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

We present a model for the thermal processing of particles in shock waves typical of the solar nebula. This shock model improves on existing models in that the dissociation and recombination of H2 and the evaporation of particles are accounted for in their effects on the mass, momentum and energy fluxes. Also, besides thermal exchange with the gas and gas-drag heating, particles can be heated by absorbing the thermal radiation emitted by other particles. The flow of radiation is calculated using the equations of radiative transfer in a slab geometry. We compute the thermal histories of particles as they encounter and pass through the shock. We apply this shock model to the melting and cooling of chondrules in the solar nebula. We constrain the combinations of shock speed and gas density needed for chondrules to reach melting temperatures, and show that these are consistent with shock waves generated by gravitational instabilities in the protoplanetary disk. After their melting, cooling rates of chondrules in the range 10-1000 K h^(-1) are naturally reproduced by the shock model. Chondrules are kept warm by the reservoir of hot shocked gas, which cools only as fast as the dust grains and chondrules themselves can radiate away the gas's energy. We predict a positive correlation between the concentration of chondrules in a region and the cooling rates of chondrules in that region. This correlation is supported by the unusually high frequency of (rapidly cooled) barred chondrules among compound chondrules, which must have collided preferentially in regions of high chondrule density. We discuss these and other compelling consistencies between the meteoritic record and the shock wave model of chondrule formation.

/pdf/a-model-of-the-thermal-processing-of-particles-in-solar-4qrj3l1sr3.pdf

A model of the thermal processing of particles in solar nebula shocks: Application to the cooling rates of chondrules

Our Solar System was formed from a cloud of gas and dust. Most of the dust mass is contained in amorphous silicates, yet crystalline silicates are abundant throughout the Solar System, reflecting the thermal and chemical alteration of solids during planet formation. (Even primitive bodies such as comets contain crystalline silicates.) Little is known about the evolution of the dust that forms Earth-like planets. Here we report spatially resolved detections and compositional analyses of these building blocks in the innermost two astronomical units of three proto-planetary disks. We find the dust in these regions to be highly crystallized, more so than any other dust observed in young stars until now. In addition, the outer region of one star has equal amounts of pyroxene and olivine, whereas the inner regions are dominated by olivine. The spectral shape of the inner-disk spectra shows surprising similarity with Solar System comets. Radial-mixing models naturally explain this resemblance as well as the gradient in chemical composition. Our observations imply that silicates crystallize before any terrestrial planets are formed, consistent with the composition of meteorites in the Solar System.

The building blocks of planets within the ‘terrestrial’ region of protoplanetary disks

The effects of dust on the propagation and dissipation of Alfvén waves in interstellar clouds

We present results for the electric fields generated in steady one dimensional flows in media having properties that obtained in the protosolar nebula. The mean neutral velocity was taken to be constant and antiparallel to an effective gravitational field, whereas the mean gas phase ion and electron velocities as well as the velocities of entrained 0.01 cm to 1 cm radius grains and submicronto micron-radius grains were calculated. The gas phase ionization structure was followed as were the charges carried by the grains. Grains were taken to be charged in collisions with gas phase ions and electrons; graingrain charge transfer due to the Elster-Geitel mechanism as well as to an unspecified additional process at a parameterized rate was included. Electric fields of sufficient strength to induce discharges, in which chondrule formation has previously been supposed to occur, were found to obtain only if the gas phase ionization rate in the nebula was almost as low as that resulting from the decay of 40K and a grain-grain charge transfer mechanism in addition to the Elster-Geitel process operated. We conclude that the existence of lightning in the protosolar nebula has to depend on the operation of unknown grain-grain charge transfer processes whereas the Elster-Geitel mechanism has proved to be completely inadequate for producing lightning there. For all but a small range of model parameters the attainment of breakdown electric field strengths requires that local ionization equilibrium has not been reached. In addition, it was found that breakdown electric field strengths were more likely to be generated if the grains had an average specific mass density not much lower than of order unity. Bearing in mind these severe constraints, we conclude that nebular lightning is possible, but requires special conditions. From considerations of the global energetics, the time scales for establishing the high field strengths plus the volume affected by discharges, we conclude that if these conditions exist lightning may have heated a large fraction of the protosolar nebula at one time or another to temperatures high enough to induce the melting of solid material. Send offprint requests to: W. Pilipp

Chondrule formation by lightning in the Protosolar Nebula

We provide an introduction to self-consistent theoretical models of interstellar dynamics in which dust is treated on a footing equal to that adopted for the description of the gaseous components of the media. Simple background material on the natures of interstellar clouds, dust, and star forming regions is given in the hopes that this review will be accessible to scientists and students interested in a broad range of nonastronomical dusty plasmas as well as to astrophysicists. The main emphasis is on the effects of dust on the damping of waves in clouds, on ambipolar diffusion in star formation, and on the structures of shocks driven into the interstellar clouds by the winds from recently formed stars.

Dusty plasmas in interstellar clouds and star forming regions

Les ondes de choc de type C sont etudiees en utilisant des traitements plus complets de l'equilibre d'ionisation, de la charge des grains, de la dynamique des grains, et de l'entrainement grain-neutre que ceux utilises anterieurement dans les modeles d'ondes de choc dans les nuages interstellaires denses.

Grains in shocks in weakly ionized clouds. I - A one fluid treatment of grain dynamics

Fluid acceleration can play a role similar to that of gravity in the establishment of charge separation generated electric fields in weakly ionized plasma in which solid particles are the dominant carriers of both negative and positive charge. It is pointed out that the properties of fluid motions, the ionization structures, and grain size and charge distributions necessary to produce electric fields strong enough to induce discharge in the absence of gravity can be inferred from calculations of the electric fields in linear acoustic waves

W. Pilipp

Papers

The effects of dust on the propagation and dissipation of Alfvén waves in interstellar clouds

Chondrule formation by lightning in the Protosolar Nebula

Dusty plasmas in interstellar clouds and star forming regions

Grains in shocks in weakly ionized clouds. I - A one fluid treatment of grain dynamics

Large Electric Fields in Acoustic Waves and the Stimulation of Lightning Discharges