Colloquium : Fundamentals of dust-plasma interactions
TL;DR: In this paper, the underlying physics of different forces that act on a charged dust grain is reviewed, including wakefield and ion focusing effects and dipole-dipole interactions between unevenly charged dust rods.
Abstract: Dusty plasmas are ubiquitous in low-temperature laboratory discharges as well as in the near-earth environment, planetary rings, and interstellar spaces. In this paper, updated knowledge of fundamentals of collective dust-plasma interactions and several novel phenomena are presented that have been observed in laboratories and in space dusty plasmas. Mechanisms that are responsible for the charging of dust grains are discussed, and the fact that the dust charge perturbation is a new dynamical variable in a dusty plasma. The underlying physics of different forces that act on a charged dust grain is reviewed. In dusty plasmas, there are new attractive forces (e.g., due to wakefield and ion focusing effects and dipole-dipole interactions between unevenly charged dust rods). Furthermore, in the presence of an ensemble of charged dust grains, there are collective dust-plasma interactions featuring new waves (e.g., the dust acoustic wave, the dust ion-acoustic wave, the dust lattice wave, etc.), new instabilities, and coherent nonlinear structures (dust acoustic and dust ion-acoustic shocks, dust voids, and dust vortices), which are also discussed. Theoretical models for numerous collective dust-plasma interactions are compared with existing observations from laboratories and space environments.
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TL;DR: Complex (dusty) plasmas are composed of a weakly ionized gas and charged microparticles and represent the plasma state of soft matter as discussed by the authors, and they can be easily manipulated in different ways, also at the level of individual particles.
Abstract: Complex (dusty) plasmas are composed of a weakly ionized gas and charged microparticles and represent the plasma state of soft matter. Complex plasmas have several remarkable features: Dynamical time scales associated with microparticles are ``stretched'' to tens of milliseconds, yet the microparticles themselves can be easily visualized individually. Furthermore, since the background gas is dilute, the particle dynamics in strongly coupled complex plasmas is virtually undamped, which provides a direct analogy to regular liquids and solids in terms of the atomistic dynamics. Finally, complex plasmas can be easily manipulated in different ways---also at the level of individual particles. Altogether, this gives us a unique opportunity to go beyond the limits of continuous media and study---at the kinetic level---various generic processes occurring in liquids or solids, in regimes ranging from the onset of cooperative phenomena to large strongly coupled systems. In the first part of the review some of the basic and new physics are highlighted which complex plasmas enable us to study, and in the second (major) part strong coupling phenomena in an interdisciplinary context are examined. The connections with complex fluids are emphasized and a number of generic liquid and solid-state issues are addressed. In summary, application oriented research is discussed.
618 citations
01 Jan 2004
TL;DR: In this paper, the authors provide an up-to-date overview of dusty plasma effects in Saturn's magnetosphere and draw attention to several outstanding problems that could be resolved by the Cassini mission.
Abstract: [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.
352 citations
TL;DR: In this article, the authors give an overview on recent experimental and theoretical results in complex plasmas, including liquid-like behavior, crystal formation, structural and dynamic properties, which is expected that many of these effects will be of interest also to researchers in other fields where strong correlations play a prominent role.
Abstract: Strong correlations—cooperative behavior due to many-particle interactions—are omnipresent in nature. They occur in electrolytic solutions, dense plasmas, ultracold ions and atomic gases in traps, complex (dusty) plasmas, electrons and excitons in quantum dots and the quark–gluon plasma. Correlation effects include the emergence of long-range order, of liquid-like or crystalline structures and collective dynamic properties (collective modes). The observation and experimental analysis of strong correlations are often difficult, requiring, in many cases, extreme conditions such as very low temperatures or high densities. An exception is complex plasmas where strong coupling can be easily achieved, even at room temperature. These systems feature the strongest correlations reported so far and experiments allow for an unprecedented precision and full single-particle resolution of the stationary and time-dependent many-particle behavior. The governing role of the interactions in strongly correlated systems gives rise to many universal properties observed in all of them. This makes the analysis of one particular system interesting for many others. This motivates the goal of this paper which is to give an overview on recent experimental and theoretical results in complex plasmas including liquid-like behavior, crystal formation, structural and dynamic properties. It is expected that many of these effects will be of interest also to researchers in other fields where strong correlations play a prominent role. (Some figures in this article are in colour only in the electronic version) This article was invited by Gordon Baym.
349 citations
TL;DR: The relevant numerical analysis of the appropriate nonlinear solution is presented and the nonlinear structure could be useful for controlling and maximizing highly energetic pulses in dusty plasmas.
Abstract: We present an investigation for the generation of a dust-acoustic rogue wave in a dusty plasma composed of negatively charged dust grains, as well as nonextensive electrons and ions. For this purpose, the reductive perturbation technique is used to obtain a nonlinear Schr\"odinger equation. The critical wave-number threshold ${k}_{c}$, which indicates where the modulational instability sets in, has been determined precisely for various regimes. Two different behaviors of ${k}_{c}$ against the nonextensive parameter $q$ are found. For small ${k}_{c}$, it is found that increasing $q$ would lead to an increase of ${k}_{c}$ until $q$ approaches a certain value ${q}_{c}$, then further increase of $q$ beyond ${q}_{c}$ decreases the value of ${k}_{c}$. For large ${k}_{c}$, the critical wave-number threshold ${k}_{c}$ is always increasing with $q$. Within the modulational instability region, a random perturbation of the amplitude grows and thus creates dust-acoustic rogue waves. In order to show that the characteristics of the rogue waves are influenced by the plasma parameters, the relevant numerical analysis of the appropriate nonlinear solution is presented. The nonlinear structure, as reported here, could be useful for controlling and maximizing highly energetic pulses in dusty plasmas.
187 citations
TL;DR: The electric potential around an isolated ion has a hard core negative part that resembles the Lennard-Jones-type potential, which will be responsible for the attraction of ions forming lattices and atoms or molecules in quantum plasmas at nanoscales.
Abstract: We report a new attractive force between ions that are shielded by degenerate electrons in quantum plasmas. Specifically, we show that the electric potential around an isolated ion has a hard core negative part that resembles the Lennard-Jones–type potential. Physically, the new electric potential is attributed to the consideration of the quantum statistical pressure and the quantum Bohm potential, as well as the electron exchange and electron correlations due to electron-1/2 spin within the framework of the quantum hydrodynamical description of quantum plasmas. The shape of the attractive potential is determined by the ratio between the Bohr radius and the Wigner-Seitz radius of degenerate electrons. The existence of the hard core negative potential will be responsible for the attraction of ions forming lattices and atoms or molecules, as well as for critical points and phase transitions in quantum plasmas at nanoscales.
163 citations
References
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TL;DR: In this paper, a balance of dust particle inertia and plasma pressure is investigated and it is shown that these waves can propagate linearly as a normal mode in a dusty plasma, and non-linearly as supersonic solitons of either positive or negative electrostatic potential.
1,940 citations
TL;DR: The processes that lead to charging of dust grains in a plasma are briefly reviewed in this article, where 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.
Abstract: 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.
1,470 citations
TL;DR: In this paper, a laser-Doppler velocimeter (LDV) study of velocity profiles in the laminar boundary layer adjacent to a heated flat plate revealed that the seed particles used for the LDV measurements were driven away from the plate surface by thermophoretic forces, causing a particle free region within the boundary layer of approximately one half the boundary-layer thickness.
Abstract: A laser-Doppler velocimeter (LDV) study of velocity profiles in the laminar boundary layer adjacent to a heated flat plate revealed that the seed particles used for the LDV measurements were driven away from the plate surface by thermophoretic forces, causing a particle-free region within the boundary layer of approximately one half the boundary-layer thickness. Measurements of the thickness of this region were compared with particle trajectories calculated according to several theories for the thermophoretic force. It was found that the theory of Brock, with an improved value for the thermal slip coefficient, gave the best agreement with experiment for low Knudsen numbers, λ/R = O(10−1), where λ is the mean free path and R the particle radius.Data obtained by other experimenters over a wider range of Knudsen numbers are compared, and a fitting formula for the thermophoretic force useful over the entire range 0 [les ] λ/R [les ] ∞ is proposed which agrees within 20% or less with the majority of the available data.
1,372 citations
TL;DR: In this article, a cylindrical or spherical electrode (collector) immersed in an ionized gas is brought to a suitable potential, it becomes surrounded by a symmetrical space charge region or "sheath" of positive or of negative ions (or electrons).
Abstract: When a cylindrical or spherical electrode (collector) immersed in an ionized gas is brought to a suitable potential, it becomes surrounded by a symmetrical space-charge region or "sheath" of positive or of negative ions (or electrons). Assuming that the gas pressure is so low that the proportion of ions which collide with gas molecules in the sheath is negligibly small, the current taken by the collector can be calculated in terms of the radii of the collector or sheath, the distribution of velocities among the ions arriving at the sheath boundary and the total drop of potential in the sheath. The current is independent of the actual distribution of potential in the sheath provided this distribution satisfies certain conditions.
1,338 citations
TL;DR: A macroscopic Coulomb crystal of solid particles in a plasma has been observed, and strongly coupled plasma theory predicts that the particles should organize in a Coulomb solid, in agreement with the observations.
Abstract: A macroscopic Coulomb crystal of solid particles in a plasma has been observed Images of a cloud of $7\ensuremath{-}\ensuremath{\mu}m$ "dust" particles, which are charged and levitated in a weakly ionized argon plasma, reveal a hexagonal crystal structure The crystal is visible to the unaided eye The particles are cooled by neutral gas to 310 K, and their charge is $g9800e$, corresponding to a Coulomb coupling parameter $\ensuremath{\Gamma}g20 700$ For such a large $\ensuremath{\Gamma}$ value, strongly coupled plasma theory predicts that the particles should organize in a Coulomb solid, in agreement with our observations
1,296 citations