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S V Vladimirov

Publications and source records attributed to S V Vladimirov.

At least 19 recordsLinked to original sources
PubMed2005

Criticality in a Vlasov-Poisson system: a fermioniclike universality class.

A model Vlasov-Poisson system is simulated close to the point of marginal stability, thus assuming only the wave-particle resonant interactions are responsible for saturation, and shown to obey the power-law scaling of a second-order phase transition. The set of critical exponents analogous to those of the Ising universality class is calculated and shown to obey the Widom and Rushbrooke scaling and Josephson's hyperscaling relations at the formal dimensionality d=5 below the critical point at nonzero order parameter. However, the two-point correlation function does not correspond to the propagator of Euclidean quantum field theory, which is the Gaussian model for the Ising universality class. Instead, it corresponds to the propagator for the fermionic vector field and to the upper critical dimensionality d(c) = 2. This suggests criticality of collisionless Vlasov-Poisson systems corresponds to a universality class analogous to that of critical phenomena of a fermionic quantum field description.

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PubMed2004

Theory of dust and dust-void structures in the presence of the ion diffusion.

A dust void is a dust-free region inside the dust cloud that often develops for conditions relevant to plasma processing discharges and complex plasma experiments. A distinctive feature of the void is a sharp boundary between the dust and dust-free regions; this is manifested especially clear when dissipation in the plasma is small and discontinuity of the dust number density appear. Here, the structure of the dust void boundary and the distribution of the dust and plasma parameters in the dust structure bordering the void is analyzed taking into account effects of dissipation due to the ion diffusion on plasma neutrals. The sharp boundary between the dust and void regions exists also in the presence of the ion diffusion; however, only derivatives of the dust density, dust charge, electron density and electric field are discontinuous at the void boundaries, while the functions themselves as well as derivatives of the ion drift velocity and the ion density are continuous. Numerical calculations demonstrate various sorts of diffusive dust void structures; the possibility of singularities in the balance equations caused by the diffusion process inside the dust structures is investigated. These singularities can be responsible for a new type of shocklike structures. Other structures are typically self-organized to eliminate the singularities. Numerical computations in this case demonstrate a set of thin dust layers separated by high density thin dust clouds similar to the multiple-layer dust structures observed in the laboratory and in the upper ionosphere. The possibility for existence of a few equilibrium positions of the void boundary is discussed.

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PubMed2004

Parametric instabilities in magnetized multicomponent plasmas.

This paper investigates the excitation of various natural modes in a magnetized bi-ion or dusty plasma. The excitation is provided by parametrically pumping the magnetic field. Here two ionlike species are allowed to be fully mobile. This generalizes our previous work where the second heavy species was taken to be stationary. Their collection of charge from the background neutral plasma modifies the dispersion properties of the pump and excited waves. The introduction of an extra mobile species adds extra modes to both these types of waves. We first investigate the pump wave in detail, in the case where the background magnetic field is perpendicular to the direction of propagation of the pump wave. Then we derive the dispersion equation relating the pump to the excited wave for modes propagating parallel to the background magnetic field. It is found that there are a total of twelve resonant interactions allowed, whose various growth rates are calculated and discussed.

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PubMed2003

Rotational modes of oscillation of rodlike dust grains in a plasma.

Three dimensional rotatory modes of oscillations in a one-dimensional chain of rodlike charged particles or dust grains in a plasma are investigated. The dispersion characteristics of the modes are analyzed. The stability of different equilibrium orientations of the rods, phase transitions between the different equilibria, and a critical dependence on the relative strength of the confining potential are analyzed. The relations of these processes with liquid crystals, nanotubing, and plasma coating are discussed.

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PubMed2003

Charge of a macroscopic particle in a plasma sheath.

Charging of a macroscopic body levitating in a rf plasma sheath is studied experimentally and theoretically. The nonlinear charge vs size dependence is obtained. The observed nonlinearity is explained on the basis of an approach taking into account different plasma conditions for the levitation positions of different particles. The importance of suprathermal electrons' contribution to the charging process is demonstrated.

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PubMed2003

Low-pressure diffusion equilibrium of electronegative complex plasmas.

A self-consistent fluid theory of complex electronegative colloidal plasmas in parallel-plate low-pressure discharge is presented. The self-organized low-pressure diffusion equilibrium is maintained through sources and sinks of electrons, positive and negative ions, in plasmas containing dust grains. It is shown that the colloidal dust grain subsystem strongly affects the stationary state of the discharge by dynamically modifying the electron temperature and particle creation and loss processes. The model accounts for ionization, ambipolar diffusion, electron and ion collection by the dusts, electron attachment, positive-ion-negative-ion recombination, and relevant elastic and inelastic collisions. The spatial profiles of electron and positive-ion-negative-ion number densities, electron temperature, and dust charge in electronegative SiH4 discharges are obtained for different grain size, input power, neutral gas pressure, and rates of negative-ion creation and loss.

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PubMed2003

Ion-acoustic waves in a complex plasma with negative ions.

A self-consistent theory of linear waves in complex laboratory plasmas containing dust grains and negative ions is presented. A comprehensive model for such plasmas including source and sink effects associated with the presence of dust grains and negative ions is introduced. The stationary state of the plasma as well as the dispersion and damping characteristics of the waves are investigated. All relevant processes, such as ionization, diffusion, electron attachment, negative-positive ion recombination, dust charge relaxation, and dissipation due to electron and ion elastic collisions with neutrals and dust particles, as well as charging collisions with the dusts, are taken into consideration.

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PubMed2003

Kinetics of plasma flowing around two stationary dust grains.

The characteristics of plasma particle kinetics in the presence of ions flowing around two stationary dust grains aligned in the direction of the flow are studied using a three-dimensional molecular dynamics simulation code. The dynamics of plasma electrons and ions as well as the charging process of the dust grain are simulated self-consistently. Distributions of electron and ion number densities, and the electrostatic plasma potential are obtained for various intergrain distances, including those much less, of the order of, and more than the plasma electron Debye length.

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PubMed2002

Vibrational modes in plasma crystals due to nonlinear temperature distribution in gas discharge plasmas.

It is shown that a nonlinear temperature distribution in gas discharge plasma leads to a specific low-frequency mode of a quasi-two-dimensional plasma crystal. Linear dispersion characteristics of the mode are obtained. The characteristics of the mode can depend strongly on the temperature gradients and therefore can be effectively controlled by the experimental conditions.

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PubMed2002

Criteria of phase transitions in a complex plasma.

New empirical rules for different phase transitions (including the melting of cubic lattices and the transitions between body-centered-cubic and face-centered-cubic structures) are proposed. The arrangements of charged macroparticles in a complex "dusty" plasma are numerically investigated for the conditions of laboratory experiments on weakly ionized gas discharges.

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PubMed2002

Stability of particle arrangements in a complex plasma.

It is shown that the stability of the vertical and horizontal confinement of colloidal "dust" particles levitating in a complex plasma appears as a nontrivial interplay of the external confining forces as well as the interparticle interactions and plasma collective processes such as the wake formation.

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PubMed2002

Quasilinear diffusion as a result of modulational instability in the pulsar plasma.

Quasilinear diffusion due to modulational instability is considered in this paper. Interaction between the high-frequency, nearly transverse O mode (or the transverse X mode) and the low-frequency, nearly longitudinal L-O mode in a pulsar magnetospheric pair plasma can lead to modulational instability. The low-frequency L-O mode is superluminal, which is not subjected to usual Landau damping, and it is possible that excess wave energy is stored in this superluminal mode. The superluminal low-frequency L-O mode can dissipate in a way similar to the process of Langmuir wave collapse, that is, it cascades from the long- to short-wavelength regimes. When the phase speed becomes less than c, the waves can be damped through various resonances. We consider, in particular, damping through cyclotron resonance, which can lead to particle acceleration. The energetic beam particles, which have a very small spread initially, can develop a high-energy distribution tail, acquiring pitch angles through quasilinear diffusion. These particles can emit gamma rays through synchrotron radiation, contributing to the observed pulsar high-energy emission.

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PubMed2001

Oscillations in a chain of rod-shaped colloidal particles in a plasma.

Oscillations in the one-dimensional chain consisting of rotatorlike particles levitating in a plasma are studied. General equations of motion for such a chain are derived. It is demonstrated that new oscillation modes associated with the rotational degrees of freedom appear for such a configuration. The dispersion characteristics of the modes are analyzed. Collective oscillations and equilibrium in lattices composed of cylindrical particles in a plasma are discussed.

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PubMed2001

Self-excited vertical oscillations in an rf-discharge dusty plasma.

A self-excited vertical oscillation of dust grains in the sheath region of an rf-discharge plasma has been observed. The variation of amplitude with pressure and input power was measured. Dramatic increase of oscillation amplitude was found for pressures below 4.5 Pa. Possible excitation mechanisms are considered.

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PubMed2001

Interaction of a rodlike charged macroparticle with a flowing plasma.

The formation of the wake potential is demonstrated for a rodlike particle in a plasma with an ion flow. The cases of various charge distributions on the rod are studied, including those contributing to the dipole momentum, and different angles between the direction of the ion flow and the rod are considered. The possibilities of the formation of lattices composed of cylindrical macroparticles in a plasma are discussed.

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PubMed2001

Mechanical model for the plasma maser effect.

A Fermi-like pinball model is proposed for the nonlinear plasma maser effect, or turbulent bremsstrahlung, in the nonlinear interaction of plasma particles and waves. The model consists of a system of many noninteracting particles bouncing elastically between two oscillating walls. The walls act as energy and momentum sources and sinks for the particles, analogous to the wave fields in a weakly turbulent plasma. The oscillation amplitudes and frequencies of the walls determine the dynamics and distribution of the particles. The resulting asymptotic velocity distributions agree qualitatively with existing weak turbulence theories. It is also found that the second wall, which simulates the effect of the nonresonant wave-particle interaction, can destroy correlations in the particle dynamics and lead to the formation of a high-energy tail in the velocity distribution.

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PubMed2001

Theory of collision-dominated dust voids in plasmas.

A dust void, i.e., the dust-free region in a dusty plasma, results from the balance of the electrostatic and plasma (such as the ion drag) forces acting on a dust particle. The properties of dust voids depend on the ratio of the void size to the mean free path of plasma ions colliding with neutral species of a weakly ionized plasma. For many plasma-processing and plasma-crystal experiments, the size of the void is much larger than the ion-neutral mean free path. The theory and numerical results are presented for such a collisional case including the situations in which the plasma is quasineutral in the void region or the plasma quasineutrality is violated, as well as the case in which the ion ram pressure is insignificant.

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