Localized excitations in dusty plasma crystals: A survey of theoretical results (original) (raw)
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Localized excitations of charged dust grains in dusty plasma lattices
New Vistas in Dusty Plasmas, 2005
The nonlinear aspects of charged dust grain motion in a one-dimensional dusty plasma (DP) monolayer are discussed. Both horizontal (longitudinal, acoustic mode) and vertical (transverse, optic mode) displacements are considered, and various types of localized excitations are reviewed, in a continuum approximation. Dust crystals are shown to support nonlinear kink-shaped supersonic longitudinal solitary excitations, as well as modulated envelope (either longitudinal or transverse) localized modes. The possibility for Discrete Breather (DB-) type excitations (Intrinsic Localized Modes, ILMs) to occur is investigated, from first principles. These highly localized excitations owe their existence to lattice discreteness, in combination with the interaction and/or substrate (sheath) potential nonlinearity. This possibility may open new directions in DP-related research. The relation to previous results on atomic chains as well as to experimental results on strongly-coupled dust layers in gas discharge plasmas is discussed.
Physics of Plasmas, 2004
The weakly nonlinear regime of transverse paramagnetic dust grain oscillations in dusty (complex) plasma crystals is discussed. The nonlinearity, which is related to the sheath electric/magnetic field(s) and to the inter-grain (electrostatic/magnetic dipole) interactions, is shown to lead to the generation of phase harmonics and, in the case of propagating transverse dust-lattice modes, to the modulational instability of the carrier wave due to self-interaction. The stability profile depends explicitly on the form of the electric and magnetic fields in the plasma sheath. The long term evolution of the modulated wave packet, which is described by a nonlinear Schrödinger-type equation (NLSE), may lead to propagating localized envelope structures whose exact forms are presented and discussed. Explicit suggestions for experimental investigations are put forward. PACS numbers: 52.27.Lw, 52.35.Fp, 52.25.Vy * Preprint; submitted to Physics of Plasmas. † On leave from: U.L.B. -Université Libre de Bruxelles, C. P. 231 Physique Statistique et Plasmas, Association Euratom -Etat Belge, Boulevard du Triomphe, B-1050 Brussels, Belgium; also at: U.L.B., Faculté des Sciences Apliquées -C.P. 165/81 Physique
Intrinsic Localized Modes (ILM) (or Discrete Breathers, DB) are localized oscillatory modes known to occur in atomic or molecular chains characterized by coupling and/or on-site potential nonlinearity. Quasi-crystals of charged mesoscopic dust grains (dust lattices), which have been observed since hardly a decade ago, are an exciting paradigm of such a nonlinear chain. In gasdischarge experiments, these crystals are subject to forces due to an externally imposed electric and/or magnetic field(s), which balance(s) gravity at the levitated equilibrium position, as well as to electrostatic inter-grain interaction forces. Despite the profound role of nonlinearity, which may be due to inter-grain coupling, mode-coupling and to the sheath environment, the elucidation of the nonlinear mechanisms governing dust crystals is still in a preliminary stage. This study is devoted to an investigation, from very first principles, of the existence of discrete localized modes in dust layers. Relying ...
Relaxation of dusty plasmas in plasma crystals
Journal of Plasma Physics, 2000
Relaxation phenomena in two-dimensional (2D) plasma crystals have been investigated, including both the self-consistent electric charge of dust particles and the electron and ion velocity distribution functions, by means of a modified 2D particle-in-cell (PIC) method. The results obtained show that the mutual interaction of dust particles in such crystals leads to special properties of the background electrons and ions due to their selective collection by dust particles during the relaxation. These electrons and ions can behave as nonideal components of dusty plasmas in plasma crystals even in cases where their numbers in the Debye cube are large. This effect is caused by their intensive charge exchange with dust particles, which provides dusty plasmas with the status of open statistical systems. The selective collection of electrons and ions by dust particles also causes their deviation from the initial equilibrium as well as the non-equilibrium evolution of the self-consistent electric charge of the dust particles. Relaxation phenomena in plasma crystals have to be taken into account in all cases of strong changes of plasma parameters, for example due to strong oscillations and waves in these crystals.
Dusty Plasmas: Elementary Processes, Examples and Possible Applications
This work presents an up-to-date account in dusty plasmas, a new field of current research's interest in applied physics and modern technology. These are complex systems containing nanometer or micrometer-sized particles suspended in plasma. Dust particles may be charged and the plasma and particles behave as plasma, following electromagnetic laws for particle up to about 10 nm or 100 nm if large charges are present. Dusty plasmas are interesting because presence of particles significantly alters the charged particle equilibrium leading to different phenomena. Electrostatic coupling between the grains can vary over a wide range so that the states of the dusty plasma can change from weakly coupled to crystalline. Such plasmas are of interest as a non-Hamiltonian system of interacting particles and as a means to study charging of dust particles in plasmas, electrostatic potential around a dust particle main forces acting on dust particles in plasmas, interaction between dust particles in plasmas, formation and growth of dust particles.
Strongly coupled dusty plasmas: Finite and extended systems
AIP Conference Proceedings, 2008
Systems of confined microspheres in a gaseous plasma environment are studied. These systems of trapped "dust" particles can form extended structures where the size of the system is much larger than interparticle distance. With specially tailored confinement potentials also finite arrangements of microspheres can be formed. In these systems the structure and dynamics dramatically depend on the exact particle number. Here, three-dimensional finite systems of microspheres, so-called Yukawa balls, are investigated and their structural properties are discussed with respect to the realized configurations of ground and metastable states. FIGURE 1. Scheme of the confinement of Yukawa balls [36]. a) A glass cube is placed on the lower electrode of an rf discharge.
Kinetic description of localized plasma structures in dusty plasmas
Czechoslovak Journal of Physics, 2004
The main objective of the paper is to determine asymptotic solutions to the initialvalue conditions for Vlasov-Ampere/Gauss system of equations that is to find the "far field" solutions. Dispersion relations are derived for longitudinal dusty plasma waves by use of linearized Vlasov equations. Assuming suitable equilibrium distributions for cold and hot charged particle/grain components, due to negligence of wave-particle interactions and assuming travelling wave "far field" solutions, fully nonlinear ODE is gained for Sagdeev potentials. We determine velocity distributions where and by use of Sagdeev potential equations we compute the solitary and double layer structures for a set of dusty plasma parameters. It has been proved [1], that Vlasov description of dusty plasmas is valid not only in the usual weakly coupled plasma regime but also in the strong-coupling limit for dusty plasmas. Deviations from both limits are to be expected for the intermediate range of coupling when Coulomb crystallization occurs.
Dynamic behaviors of dust particles in the plasma–sheath boundary
Physics of Plasmas, 2001
A variety of dynamic behaviors in dusty plasmas is expected under the experimental condition of weak friction with gas molecules. The device ''KAGEROU'' provides such an environment for dynamic collective phenomena. Self-excited dust oscillations in Coulomb crystals have been observed at low values of plasma density and gas pressure. An instability mechanism was identified to be delayed charging in an inhomogeneous equilibrium dust charge in the sheath. The theoretical growth rate was formulated in relation to the destabilization of a transverse dust lattice wave ͑T-DLW͒, which was found to be very sensitive to the presence of a small amount of hot electrons which produces a substantial positive equilibrium charge gradient ٌQ d-eq around the equilibrium position of dust particles in the plasma-sheath boundary. The first experimental observation of a correlated self-excited vertical oscillations in a one-dimensional dust chain indicates a destabilization of T-DLW. The experimental condition is very consistent with the parameter area which predicts numerically an instability of T-DLW.
Two-dimensional dusty plasma crystals and liquids
Journal of Physics: Conference Series, 2009
Strongly coupled plasmas -in which the average potential energy per particle dominates over the average kinetic energy -appear in a wide variety of physical systems. Among these systems, dust plasma crystals and liquids realized in low-pressure gas discharges by dispersing mesoscopic grains into the plasma have attracted a lot of attention during the past years. We describe the experimental realization of the quasi-two-dimensional dust system, summarize the basics of the computer simulation and theoretical approaches capable of their description in the liquid and solid phases. We discuss the properties of the dynamical density and current correlation spectra, generated by molecular dynamics simulations, and address the issues associated with the existence of different phases and transport coefficients (e.g. superdiffusive behavior) in the low-dimensional systems under study.