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The PlasmaKristall-4 (PK-4) experiment on the International Space Station (ISS) has been widely used to study collective behavior and self-organization of dust grains immersed in a plasma environment under microgravity conditions. Recently it has been shown that the PK-4 BU, a ground-based replica of the PK-4, supports the presence of inhomogeneous features related to ionization waves moving through the positive column on the microsecond timescale 1 . Plasma conditions within the ionization waves, such as plasma density and electric fields, have been shown to vary by up to an order of magnitude from background values. Previous investigations of dust dynamics within the PK-4 environment have focused on time-averaged plasma conditions, assuming a homogeneous environment. Given the importance of plasma density and electric fields for dust self-organization, it is important to understand the impact of their observed variability. Here results will be presented from an N-body simulation which models dust and ion dynamics, employing initial boundary conditions derived from a 2D particle-in-cell with Monte Carlo collisions (PIC/MCC) simulation of the observed ionization waves.

The role of charged, solid particulate matter (i.e., "dust"’ in plasmas has been considered for several decades. However, beginning with observations of structures in the dust tails of comets and the Voyager observations of radial structures ("spokes"’ in Saturn’s rings, the role of charged dust in the solar system led to the emergence of the field of "dusty" (alternatively, "complex"’ plasmas. Since the early 1990’s there has been a complementary effort in the area of laboratory dusty plasmas that has, over almost four decades, led to the observation of numerous types of plasma and dusty plasma behavior – ranging from appearance of strongly-coupled, self-organized dusty plasma crystals to new types of collective, dust-driven modes, such as the dust acoustic and dust density waves.

The excitation of low frequency dust acoustic (or dust density) waves in a dusty plasma can be driven by the flow of ions relative to dust. We consider the nonlinear development of the ion–dust streaming instability in a highly collisional plasma, where the ion and dust collision frequencies are a significant fraction of their corresponding plasma frequencies. This collisional parameter regime may be relevant to dusty plasma experiments under microgravity or ground-based conditions with high gas pressure. One-dimensional particle-in-cell simulations are presented, which take into account collisions of ions and dust with neutrals, and a background electric field that drives the ion flow. Ion flow speeds of the order of a few times thermal are considered. Waveforms of the dust density are found to have broad troughs and sharp crests in the nonlinear phase. The results are compared with the nonlinear development of the ion–dust streaming instability in a plasma with low collisionality.

The physics of dusty plasmas in high magnetic field is an area of current interest, spurred by the development of experiments in this area. Dust acoustic (or dust density) waves have been observed in many laboratory dusty plasmas where there is either no or weak magnetic field. These waves may be excited by the flow of ions relative to dust. The effects of high magnetic field on the excitation of dust waves have been considered in the theoretical literature, including instabilities driven by ions streaming either along or across the magnetic field. We review and extend prior theory work on such instabilities, exploring their behavior as the magnetization of the ions is varied, while the electrons are strongly magnetized and the dust is unmagnetized. It is shown that when the ions are magnetized, there can be structure in the unstable wavenumber spectrum under certain conditions. Application to possible experimental parameters is discussed.

The PK-4 system is a micro-gravity dusty plasma experiment currently in operation on-board the International Space Station. The experiment utilizes a long DC discharge in neon or argon gases. We apply our 2D particle-in-cell with Monte Carlo collisions discharge simulation to compute local plasma parameters that serve as input data for future dust dynamics models. The simulation includes electrons, Ne+ ions, and Ne m metastable atoms in neon gas and their collisions at solid surfaces including secondary electron emission and glass wall charging. On the time scale of the on-board optical imaging, the positive column appears stable and homogeneous. On the other hand, our simulations show that on microsecond time scales the positive column is highly inhomogeneous: ionization waves with phase velocities in the range between 500 m s−1 and 1200 m s−1 dominate the structure. In these waves, the electric field and charged particle densities can reach amplitudes up to 10 times of their average value. Our experiments on ground-based PK-4 replica systems fully support the numerical findings. In the experiment, the direction of the DC current can be alternated, which has been found to favor dust particle chain formation. We discuss possible mechanisms for how the highly oscillatory plasma environment contributes to the dust particle chain formation.

The nonlinear development of a low frequency beam-cyclotron instability in a collisional plasma composed of magnetized ions and electrons and unmagnetized, negatively charged dust is investigated using one-dimensional particle-in-cell simulations. Collisions of charged particles with neutrals are taken into account via a Langevin operator. The instability, which is driven by an ion $\boldsymbol{E}\times \boldsymbol{B}$ drift, excites a quasi-discrete wavenumber spectrum of waves that propagate perpendicular to the magnetic field with frequency of the order of the dust plasma frequency. In the linear regime, the unstable wavelengths are of the order of the ion gyroradius. As the wave energy density increases, the dominant modes shift to longer wavelengths, suggesting a transition to a Hall-current-type instability. Parameters are considered that reflect the ordering of plasma and dust quantities in laboratory dusty plasmas with high magnetic field. Comparison with the nonlinear development of this beam cyclotron instability in a collisionless dusty plasma is also briefly discussed.

A description is given of the Magnetized Dusty Plasma Experiment (MDPX) at Auburn University that was designed to study the physics of highly magnetized low temperature plasmas and magnetized dusty plasmas. The central components of the MDPX are a superconducting solenoid capable of operation at magnetic fields up to 4 T, and a parallel plate RF discharge plasma. Results from some of the initial experiments will be presented.A description is given of the Magnetized Dusty Plasma Experiment (MDPX) at Auburn University that was designed to study the physics of highly magnetized low temperature plasmas and magnetized dusty plasmas. The central components of the MDPX are a superconducting solenoid capable of operation at magnetic fields up to 4 T, and a parallel plate RF discharge plasma. Results from some of the initial experiments will be presented.

Recently it has been proposed to alter the interaction between dust grains in a plasma by applying ac electric fields to distort the Debye spheres surrounding the grains, which may lead to interaction potentials with a Lennard-Jones form under certain conditions (e.g., Kompaneets et al., Phys. Plasmas 16, 043705 (2009)). Motivated by this, we consider the dispersion relations of longitudinal and transverse waves in a dusty plasma liquid where the grains interact via a Lennard-Jones potential. We use the Quasi-Localized Charge approximation combined with an analytic expression for the pair distribution function for Lennard-Jones fluids (Matteoli and Mansoori, J. Chem. Phys. 103, 4672 (1995)). Possible dusty plasma experimental parameters are considered. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The Magnetized Dusty Plasma Experiment (MDPX) device is a newly constructed research instrument for the study of dusty (complex) plasmas. The MDPX device is envisioned as an experimental platform in which the dynamical behavior of all three charged plasma components, the electrons, ions, and charged microparticles (i.e., the ‘dust’) will be significantly influenced by the magnetic force. This brief paper will provide a short overview of the design, magnetic performance, and initial plasma measurements in the MDPX device.

The last decade has seen the development of new experimental devices to explore the physics of magnetized dusty plasmas. Because of the small charge-to-mass ratio of the charged microparticles, it is necessary to operate these experiments at high magnetic fields of several Tesla in order to observe the direct effect of the magnetic forces on the transport properties of the charged microparticles. While the study of magnetized dusty plasmas is still the ultimate goal, these experiments have also provided new opportunities to studies regimes of strongly magnetized, low temperature, laboratory plasmas that have not been extensively explored. Experiments show the formation of new types of self- and imposed-ordered structures that form in both the plasma and among the microparticles. This paper summarizes recent experimental observations of plasma filamentation (in the plasma) and will discuss possible connections to 'dust gridding' phenomena that are observed in the magnetized dusty plasma experiment device.

We report experimental observations of a low-frequency (≪ ion gyrofrequency) electrostatic wave mode in a magnetized cylindrical (Q machine) plasma containing positive ions, very few electrons and a relatively large fraction (n−/ne > 103) of heavy negative ions (m−/m+ ≈ 10), and no magnetic field-aligned current. The waves propagate nearly perpendicular to B with a multiharmonic spectrum. The maximum wave amplitude coincided spatially with the region of largest density gradient suggesting that the waves were excited by a drift instability in a nearly electron-free positive ion–negative ion plasma

Drift wave instability in a magnetized plasma composed of positive ions and negative ions is considered using linear kinetic theory in the local approximation. We consider the case where the mass (temperature) of the negative ions is much larger (smaller) than that of the positive ions, and where the gyroradii of the two ion species are comparable. Weak collisional effects are taken into account. Application to possible laboratory parameters is discussed.

Dust acoustic (or dust density) waves have been observed in many laboratory dusty plasmas. These low-frequency waves involve the dynamics of highly charged and massive dust grains, and can be excited by the flow of ions relative to dust. In this paper, we consider the nonlinear development of the dust acoustic instability, excited by thermal ion flow, in a collisional plasma containing dust with high kinetic temperature (warm dust). It is shown that under certain conditions there may be a long-wavelength secondary instability in the nonlinear stage as dust gets heated by the waves. The characteristics of the nonlinear development are considered as a function of the relative charge density of the dust. Application to possible experimental parameters is discussed.

We consider theoretically the possible wavelength selective absorption of mid or far infrared radiation in a plasma containing micrometer-sized dust grains having surface phonon resonances in these wavelength regimes. Issues related to grain heating and charging are also discussed.

One dimensional Particle in Cell simulations of a dust- dust counter-streaming instability in a plasma containing dust grains of opposite charge polarity are presented. This dust-dust instability has potentially the lowest threshold drift for a dust wave instability in an unmagnetized dusty plasma. The linear and nonlinear development of the dusty plasma instability is investigated, including the effects of collisions with background neutrals, and a background electric field which acts as a driver to impart the drift velocities of the counter streaming charged dust particles. The saturation of the linear instability appears to be dust heating related to dust trapping. Potential double layer formation from dust-dust turbulence is observed in cases with a high neutral collision rate. A comparative study is done with varying collision rates and background electric fields to explore the nonlinear development as a function of collision rate and background electric field. These simulation results could help guide future laboratory and micro-gravity dusty plasma experiments on this instability. The results could also relate to similar counter-streaming instabilities in pair plasmas and negative ion plasmas

It is generally assumed that negatively charged icy dust particles in the mesosphere are charged by the collection of thermal plasma particles. However, there are some indications that there may be a population of hyperthermal electrons in the D-region under auroral activity under certain conditions (e.g. Margot-Chaker and McNamara, Planetary and Space Science 32, 391, 1984). In this brief communication, we speculate on the effect of a hyperthermal distribution of electrons on dust charging, and how this might affect prevailing turbulence scattering theory for polar summer mesophere echoes.

A strongly coupled Yukawa liquid is a system of charged particles which interact via a screened Coulomb interaction and in which the electrostatic energy between neighboring particles is larger than their thermal energy but not large enough for crystallization. Various plasma systems including ultracold neutral plasmas and complex (dusty) plasmas can exist in this strongly coupled liquid phase.Here we investigate instabilities driven by the relative streaming of plasma components in three-dimensional Yukawa liquids with a focus on complex plasmas. This includes a dust acoustic instability driven by weakly coupled ions streaming through the dust liquid, and a dust-dust instability driven by the counter-streaming of strongly coupled dust grains. Compared to the Vlasov behavior we find there can be a substantial modification of the unstable wavenumber spectrum due to strong coupling effects (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ion waves excited by charged dust beams streaming across or along the geomagnetic field in the ionosphere may be generated by plasma instabilities during aerosol release experiments. The injection speed of the dust and gas is comparable to or larger than the ion thermal speed in the background plasma. The dust grains can get charged by plasma collection from the ambient ionosphere, and can thus act as a charged beam that excites instabilities in the background plasma. The theory is applied to relatively early time scales of the order of ∼0.1–1s in the dust–gas cloud expansion, with wave frequencies that are larger than the ion gyrofrequency, and collisions with neutrals are included.

Dusty plasmas have been studied in argon, radio frequency (rf) glow discharge plasmas with magnetic fields up to 1.5 T. Plasmas were formed between a powered bottom electrode and a grounded top electrode in which an aluminum wire mesh is fixed in the center. This work will examine the experimental conditions at which imposed, ordered structures form within the dusty plasma. These imposed, ordered structures, as reported in earlier works, are characterized by the alignment of dust particles to the spatial structure of the wire mesh in the top electrode and occur at high magnetic fields (B ≥ 1 T) and low neutral pressure (P ≤ 100 mTorr). A pair of parameters will be established to characterize the degree to which the dust particles are affected by these imposed ordered structures on both long and short time scales. Using these parameters, it will be shown that a correlation exists between the onset of imposed, ordered structures and the magnetization of ions within the plasma.Dusty plasmas have been studied in argon, radio frequency (rf) glow discharge plasmas with magnetic fields up to 1.5 T. Plasmas were formed between a powered bottom electrode and a grounded top electrode in which an aluminum wire mesh is fixed in the center. This work will examine the experimental conditions at which imposed, ordered structures form within the dusty plasma. These imposed, ordered structures, as reported in earlier works, are characterized by the alignment of dust particles to the spatial structure of the wire mesh in the top electrode and occur at high magnetic fields (B ≥ 1 T) and low neutral pressure (P ≤ 100 mTorr). A pair of parameters will be established to characterize the degree to which the dust particles are affected by these imposed ordered structures on both long and short time scales. Using these parameters, it will be shown that a correlation exists between the onset of imposed...

We present a kinetic theory analysis of the electrostatic ion cyclotron (EIC) instability in a plasma containing positive ions, electrons, and negative ions that are much more massive than the positive ions. Conditions are investigated for exciting the fundamental and the higher harmonic EIC waves associated with each ion species. We find that as the concentration of heavy negative ions increases, the wave frequencies increase, the unstable spectrum in general shifts to longer perpendicular wavelengths, and the growth of higher harmonic EIC waves tends to increase within certain parameter ranges. Applications to possible laboratory plasmas are discussed.

Velocity distribution functions of dust particles of various sizes are simulated in different regions of a tokamak using the DUSTT code. It is shown that dust particles accelerated by plasma flows can reach very high speed >1 km/s at the terminal stages of vaporization. Collisions of beryllium and tungsten dust particles with beryllium wall are modeled with the LS-DYNA material structural analysis code. It is demonstrated that the collisions at high speed ∼1 km/s can cause significant damage to the wall or complete dust destruction depending on dust and wall material parameters.

In this work we analyze the size (radius) distribution function of dust particles in tokamak plasmas during a steady state discharge. A relation between the radius distribution function of dust in the plasma and the radius distribution of dust injected from tokamak walls is obtained using a Green's function formalism. Numerical simulations of the dust radius distribution function in a tokamak plasma with the Dust Transport (DUSTT) code are used to obtain the analytical form of the Green's function semi-empirically. It is demonstrated that the Green's function obtained can be used to predict qualitatively the dust size distributions in the tokamak plasmas. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Recently, there has been interest in the properties of strongly coupled dusty plasmas in the liquid phase. Here, we consider theoretically a possible way to generate and detect a dense dusty plasma liquid. The idea is to use noble metal submicron dust particles and detect the dust by scattering at the surface plasmon resonance frequency of the dust. Parameters that may be relevant to possible laboratory dusty plasma experiments are discussed.

The ion-acoustic instability in a dusty negative ion plasma is investigated, focusing on the parameter regime in which the negative ion density is much larger than the electron density. The dynamics of the massive dust grains are neglected, but collisions of electrons and ions with dust grains in addition to other collisional processes are taken into account. The presence of a population of charged dust can change the frequency of the fast wave, lead to additional damping due to ion–dust collisions, and change the conditions for wave growth. Applications to dusty negative ion plasmas in the laboratory and in space are discussed.

The beam-plasma instability displays new properties when either the beam or the plasma, or both, are strongly interacting. We have considered theoretically the case when the plasma is in the crystalline phase and forms a lattice, and the beam is moving in the lattice plane. We consider a 2-D plasma crystal in which both the grains and the beam particles interact through a realistic Yukawa potential. The beam particles are assumed to be weakly coupled to each other and to the lattice. Using the full phonon spectrum for a 2-D hexagonal Yukawa lattice, we determine and compare the transverse and longitudinal growth rates. The relationship between the beam speed and the longitudinal and transverse sound speeds, and the direction of the beam with respect to the principle axes of the lattice determine the qualitative behavior of the growth rates. For beam speeds between the longitudinal and transverse sound speeds, the transverse instability could be more important, because it appears at lower wavenumbers

The magnetized dusty plasma experiment (MDPX) is a newly commissioned plasma device that started operations in late spring, 2014. The research activities of this device are focused on the study of the physics, highly magnetized plasmas, and magnetized dusty plasmas. The design of the MDPX device is centered on two main components: an open bore, superconducting magnet that is designed to produce, in a steady state, both uniform magnetic fields up to 4 Tesla and non-uniform magnetic fields with gradients of 1–2 T m−1and a flexible, removable, octagonal vacuum chamber that provides substantial probe and optical access to the plasma. This paper will provide a review of the design criteria for the MDPX device, a description of the research objectives, and brief discussion of the research opportunities offered by this multi-institution, multi-user project.

The well-known problem of beam–plasma instability acquires new aspects when one or both of the two components (the beam and the plasma) are strongly interacting. We have now theoretically considered the case when the plasma is in the solid phase and forms a lattice. In this situation, the inherent anisotropy of the lattice leads to a coupling between the longitudinal and transverse polarizations. One of the novel features of the beam–plasma instability in this scenario is the possible excitation of transverse modes, which should be an experimentally observable signature of the instability. We have initially concentrated on a 2D toy model with the beam lying in the lattice plane. At the same time, we have initiated a molecular dynamics simulation program for studying various aspects of the penetration of a beam into a plasma lattice. The beam parameters can be adjusted in order to see the effects of increasing coupling strength within the beam and to distinguish between collective phenomena and scattering on individual particles. When both components are strongly interacting, a number of remarkable phenomena—trapping of beam particles, creation of dislocations, local melting of the lattice—may be observed.

The conventional Vlasov treatment of beam-plasma instabilities is inappropriate when the plasma is strongly coupled. In the strongly coupled liquid state, the strong correlations between the dust grains fundamentally affect the conditions for instability. In the crystalline state, the inherent anisotropy couples the longitudinal and transverse polarizations, and results in unstable excitations in both polarizations. We summarize analyses of resonant and non-resonant, as well as resistive instabilities. We consider both ion-dust streaming and dust beam-plasma instabilities. Strong coupling, in general, leads to an enhancement of the growth rates. In the crystalline phase, a resonant transverse instability can be excited.

This note investigates an ion-dust streaming instability with frequency ω less than the dust collision frequency νd, in an unmagnetized collisional dusty plasma. Under certain conditions, a resistive instability can be excited by an ion drift on the order of the ion thermal speed, even when the dust acoustic wave is heavily damped. The effect of weak collisions on the usual dust acoustic instability in the regime ω > νd is also considered. Applications to experimental observations of low-frequency fluctuations in laboratory d.c. glow discharge dusty plasmas are discussed.

Wave dispersion relations in the strongly coupled liquid phase of a two-dimensional system of dust grains interacting via both Yukawa and dipole interactions are investigated. The model system comprises a layer of charged superparamagnetic grains in a plasma in an external, uniform magnetic field B whose magnitude and direction can be varied. Because the induced magnetic dipole moments of the grains lie along B, the interaction between the grains becomes anisotropic as B is tilted with respect to the layer. The theoretical approach uses a reformulated quasilocalized charge approximation that can treat dipole interactions, combined with molecular dynamics simulations. The mode dispersion relations are found to depend on the relative strengths of the Yukawa and dipole interactions and the direction of wave propagation in the plane.

Theoretical studies of dusty plasmas have been performed by focusing attention principally on collective phenomena and on grain motion. This thesis consists of a collection of seven published papers that explore both the collective behavior of a complex plasma system as well as the dynamics of grains in plasmas. In paper 1, a mechanism that explains the energy gain which leads to the self excited grain oscillations is theoretically formulated. The newly developed mechanism explains the observed self excited oscillations through the coupling of plasma sheath fluctuations with the electrostatic force, which holds the dust grain. In paper 2, theoretical and simulation studies have been conducted to study the vertical oscillations of dust grains that are levitated in plasma sheaths, under low pressure conditions. The oscillations were driven either by an external force or by a plasma number density modulation. The proposed model gives a full picture of the dust grains dynamics and is capable of successfully explaining the experimental observations. Paper 3 explores both theoretically and numerically the origin of the nonlinearities that lead to the observed oscillation resonances. The feature of the confining potential well which traps the grain, the influence of an electrode voltage modulation on the trapping well, and hence on the grain dynamics, and the resulting nonlinear resonances are analyzed in detail. The numerical simulations presented successfully reproduce a broad range of dynamical phenomena, including the self excited oscillations, for a range of different parameters. Paper 4 is dedicated to the analysis of the propagation of Dust Acoustic Waves (DAW) in a medium with an equilibrium dust density distribution. It has been theoretically shown that only some harmonics of the dust density distribution will influence the propagation of the DAW, thus modifying its frequency. Paper 5 presents a theoretical and numerical analysis of the excitation of higher harmonics of electrostatic dust cyclotron waves. The instability is driven by the ion and electron currents flowing along the magnetic field. The dispersion relation and the wave instability conditions have been derived, and a detailed numerical analysis has been performed. In Paper 6, we explore theoretically some cross field instabilities of low frequency, long wavelength electrostatic modes in fully and weakly ionized plasmas. It is shown that in a magnetoplasma with a transverse equilibrium dc electric field, the energy associated with the cross field motion of the plasma particles can be coupled to low frequency electrostatic waves. Paper 7 explores the properties and instabilities of low frequency electrostatic waves propagating in a current carrying magnetoplasma with equilibrium density and field aligned ion flow with a transverse gradient. The paper contains previous results as limiting cases, together with additional instabilities related to the equilibrium plasma density distribution.

We use molecular dynamics (MD) and particle-in-cell (PIC) simulation methods, in which dust grains are treated as discrete particles and the background plasma is included in the potential shielding (MD) or as a Boltzmann fluid (PIC), to investigate dust-acoustic waves in a one-dimensional, strongly coupled (with the Coulomb coupling parameter {Gamma} equal to the ratio of the Coulomb energy to the thermal energy, which is greater than 1) dusty plasma. We study cases both where the dust is represented by a small number of simulation particles that form into a regular array structure at large {Gamma} (crystal limit) and where the dust is represented by a much larger number of particles (fluid limit). We show that the measured frequency for dust acoustic waves satisfies either a fluidlike dispersion relation or a lattice wavelike dispersion relation, depending on {Gamma} and the number of simulation particles. Other PIC simulations, either with plasma ions represented as particles rather than as a Boltzmann fluid or with collisions between the dust and the background gas, have also been carried out and shown to agree with theoretical predictions. Numerical issues associated with smoothing of the accumulated charge density in PIC simulations have also been addressed; smoothingmore » is shown to affect wave dispersion at high wave numbers in the fluid limit and low wave numbers in the crystal limit. {copyright} {ital 1999} {ital The American Physical Society}« less

In this paper, we consider theoretically conditions for forming crystals of positively charged dust, when the dust is heated by a laser or by a strong infrared source and emits electrons thermionically. We discuss parameters for grains dispersed in an inert gas at pressure of a few mbar. We briefly discuss levitation by forces associated with gas flow or photon flux. A possible experimental scheme for achieving such a crystal is briefly outlined.

The effect of charged dust on the Farley-Buneman instability is investigated. Linear kinetic theory is used to estimate the critical electron drift in the presence of either negatively or positively charged dust. The charge-to-mass ratio of the dust is much smaller than that of the ions, and the dust influences the instability through its effect on equilibrium charge neutrality. It is shown that in certain regimes, the critical drift can decrease as the charge density carried by negatively charged dust increases. Possible application to dusty plasmas in the upper D/lower E region boundary region of the Earth's ionosphere is discussed.

We study the nonlinear behavior of the low-frequency dust acoustic instability in a collisional dusty plasma by means of particle simulations. The instability arises due to the streaming of plasma ions and neutrals relative to charged dust grains. According to linear theory, the presence of collisions between the plasma ions and a neutral gas background reduces the growth rate of the instability. Nonlinearly, however, the presence of drifting neutrals maintains the initial relative drift between plasma and dust ions until the unstable waves grow to large amplitude and collisions due to wave-particle interactions exceed the neutral collisions. As a result, stronger nonlinear effects, as manifested by enhanced fluctuations, larger amounts of plasma and dust heating, and a temporary reduction of the relative drift velocity, can occur in the presence of collisions.

A dusty (or complex) plasma is a four-component plasma system consisting of electrons, ions, neutral atoms, and charged, nanometer to micrometer-sized particles (i.e., the “dust”). Because these dust grains are charged, they fully participate in the plasma dynamics and can be used to reveal details about transport, instabilities, and charging properties of plasmas. However, one important area that has not been studied extensively is the area of magnetized dusty plasmas. Even though the charged dust grains in a typical laboratory experiment can acquire several thousand elementary charges, the large mass of the grains ensures that the charge-to-mass ratio is quite low. As a result, it is technically challenging to design an experiment that can achieve full magnetization of ions, electrons, and the charged dust grains.

In a plasma containing charged dust grains, the dust acoustic instability (DAI) can be driven by ions streaming through the dust with speed less than the ion thermal speed. When the dust is strongly coupled in the liquid phase, the dispersion relation of the dust acoustic modes changes in a way that leads to an enhancement of the growth rate of the DAI. In this paper, we show how strong coupling enhances the DAI growth rate and consider application to microgravity experiments where subthermal ion flows are in general possible.

The use of ultraviolet (UV) radiation to reduce the negative charge on dust particles and modify force balance in particle traps in processing plasmas is investigated theoretically. Possible photophoresis associated with the UV flux is also discussed. The use of UV to facilitate moving contaminant particles from traps is considered.

A scheme for forming a Coulomb lattice of positively charged dust grains in a high-pressure (P>torr) gas is discussed theoretically. The grains are charged positively by photoemission in the presence of a flux of ultraviolet (UV) photons with energy larger than the work function of the grains, but lower than the ionization potential of the background gas. Methods for levitating and containing the dust using photophoretic forces (both UV and non-UV), gas drag, and electrostatic forces are considered.

Modified two-stream instabilities are investigated in dusty plasmas in which electrons and/or ions drift across an external magnetic field. The usual high requency instability ( ω ce ⪢ ω ⪢ ω ci ) driven by treaming electrons is modified due to n i ≠ n e . Low frequency instabilities in the regime ω ci ⪢ ω ⪢ ω cd ( ω cd is the dust gyrofrequency) are considered for both long wavelengths, kϱ i ⪡ 1, and short wavelengths, kϱ i ⪢ 1 ( ϱ i is the ion gyroradius). It is found that low frequency instability can occur even when T i ⪢ T e . Applications of the results to dusty plasmas in protostellar clouds and planetary rings are discussed.

The effect of charged dust on the collisionless electrostatic ion cyclotron instability is investigated. Standard linear Vlasov theory is used to estimate the critical electron drift in the presence of either positively or negatively charged dust. The dust is assumed to be uniform in both mass and charge with the dust mass much greater than the ion mass. It is shown that the critical drift decreases as the charge density carried by negatively charged dust increases. Possible applications to the current system connecting Jupiter and its satellite Io, as well as that of the Saturnian rings are discussed.

The Magnetized Dusty Plasma Experiment at Auburn University has been operational for over one year. In that time, a number of experiments have been performed at magnetic fields up to B = 2.5 T to explore the interaction between magnetized plasmas and charged, micron-sized dust particles. This paper reports on the initial results from studies of: (a) the formation of imposed, ordered structures, (b) the properties of dust wave waves in a rotating frame, and (c) the generation of plasma filaments.

High frequency drift instabilities with ωce ⪢ ω ⪢ ωci are investigated in a dusty magnetized plasma in which locally there is an electron density gradient which is opposite in sign to a dust density gradient. Two different equilibria are considered, characterized by ρ d ≶ L nd , where ρd is the dust gyroradius and Lnd is the dust density scale length. Possible application to Saturn's F-ring is discussed.

A previous model for secondary electron emission from small grains is modified to calculate yields for micron sized grains, both spherical and cylindrical, when the primary electrons constitute a high energy parallel beam. It is found that, in general, the secondary electron yield is significantly higher than for the case of normal incidence. Moreover, the equilibrium potentials of the grain are always positive due to this enhanced secondary emission. These results are compared with experimental data recently available for micron sized glass particles, and equilibrium potentials, calculated based on the model presented here, and are found to be in reasonably good agreement with their measured potentials. >

It is shown that, for a moderately long time scale, two‐body collisions can actually help in maintaining a non‐Maxwellian ion velocity distribution in a plasma. This effect occurs when the ions have orbits large enough to transit spatial regions with different physical parameters in a single collision time. The effect is applied to ions confined in a spherically convergent ion focus (SCIF), where collisions at the edge of a spherical potential well help maintain convergent non‐Maxwellian flow in the rest of the device.

A brief, critical review of dust-plasma interactions in the cosmic environment is presented, with emphasis on certain results. Both single-particle (e.g., gravitoelectrodynamics) and collective (e.g., appearance of new wave models) effects are discussed and some areas in which further research is needed are pointed out. The pressing need for laboratory studies, both to provide the necessary data for the theoretical studies and to test the predictions of these theories, is emphasized. >

A classical dusty plasma experiment was performed using two different dust grain sizes to form a strongly coupled asymmetric bilayer (two closely spaced interacting monolayers) of two species of charged dust particles. The observation and analysis of the thermally excited particle oscillations revealed the collective mode structure and wave dispersion in this system; in particular the existence of the theoretically predicted $k=0$ energy (frequency) gap was verified. Equilibrium molecular dynamics simulations were performed to emulate the experiment, assuming Yukawa type inter-particle interaction. The simulations and analytic calculations based both on lattice summation and on the QLCA approach are in good agreement with the experimental findings and help identifying and characterizing the observed phenomena., Submitted to PRL

We consider a 2D Yukawa lattice of grains, with a beam of other charged grains moving in the lattice plane. In contrast to Vlasov plasmas, where the electrostatic instability excited by the beam is only longitudinal, here both longitudinal and transverse instabilities of the lattice phonons can develop. We determine and compare the transverse and longitudinal growth rates. The growth rate spectrum in wave number space exhibits remarkable gaps where no instability can develop. Depending on the system parameters, the transverse instability can be selectively excited.

Recently there has been interest in the properties of dusty negative ion plasmas, including dust charging and collective behavior. Electronegative dusty plasmas are of interest from the perspective of both basic physics and applications. Because the addition of negative ions to a dusty plasma can change the dust charge state, and add new sources of free energy such as ion currents, such plasmas could provide useful tools with which to study the physics of dust wave instabilities. Moreover, electronegative dusty plasmas can occur in industrial processing plasma devices, where the control of dust is an issue.