Biomedical subjects

V V Yaroshenko

Publications and source records attributed to V V Yaroshenko.

9 recordsLinked to original sources

PubMed2005

Particle charge in the bulk of gas discharges.

An experimental determination of particle charge in a bulk dc discharge plasma covering a wide range of neutral gas pressures, was recently reported [S. Ratynskaia, Phys. Rev. Lett. 93, 085001 (2004)]. The charges obtained were several times smaller than the predictions of collisionless orbital motion limited theory. This discrepancy was attributed to the effect of ion-neutral collisions. In the present paper a more detailed description of this experiment is provided and additional experimental results obtained with particles of different sizes are reported. The measurements are compared with molecular dynamics simulations of particle charging for conditions similar to those of the experiment, with other available experimental data on particle charge in the bulk of gas discharges, and with a simple analytical model accounting for ion-neutral collisions. All the considered evidence indicates that ion-neutral collisions represent a very important factor, which significantly affects (reduces) the particle charge under typical discharge conditions.

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PubMed2005

Coupled dust-lattice modes in complex plasmas.

The coupling between transverse and longitudinal dust-lattice modes due to the particle-wake interactions and vertical dust charge gradient is considered. It is shown that the dust-lattice waves can be subjected to a specific instability, the criterion for which has been derived. This instability can explain experimentally observed spontaneous excitation of vibrational modes in a plasma crystal when the pressure is decreased below a critical value.

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PubMed2004

Electrostatic modes in collisional complex plasmas under microgravity conditions.

A linear dispersion relation in a highly collisional complex plasma, including ion drift, was derived in the light of recent PKE-Nefedov wave experiment performed under microgravity conditions onboard the International Space Station. Two modifications of dust density waves with wave frequencies larger than the dust-neutral collision frequency were obtained. The relevance to the space observations was analyzed and a comparison of theory and observations was made for two different complex plasma domains formed by small and large microparticles. Good qualitative agreement is found between the measurements and the theoretical dispersion relations. This allows a determination of the basic complex plasma parameters.

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PubMed2004

Vertical oscillations of paramagnetic particles in complex plasmas.

Vertical vibrations of a single magnetized dust grain and a one-dimensional string of magnetized particles in discharge plasmas are treated taking into account the magnetic force associated with gradients of an external magnetic field. For a single particle a novel type of oscillation associated with these gradients is found. Such vibrations can be stable or unstable depending on the distribution of the magnetic field inside the particle cloud. In a one-dimensional particle string the magnetic force causes a new low-frequency oscillatory mode which is characterized by inverse optical-like dispersion when the wavelength far exceeds the intergrain distance. The study of vertical vibrations of magnetized grains provides a tool for determining complex plasma parameters.

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PubMed2003

Jeans instability in partially ionized self-gravitating dusty plasmas.

By employing the Boltzmann distributions for electrons and ions and by retaining the full dynamics of charged dust and neutral fluids, we derive a dispersion law for coupled dust-acoustic and neutral sound waves in partially ionized self-gravitating dusty plasmas. This dispersion law exhibits new classes of Jeans instability in both collisionless and highly collisional regimes. The result should help understand the origin of molecular cloud collapse in interstellar space.

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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

Low-frequency electrostatic waves in self-gravitating dusty plasmas with dust-ion collisions.

The influence of dust-ion collisions on low-frequency modes in a self-gravitating dusty plasma is studied. The stability of the system is easily determined using elementary principles of rootlocus theory. It shows that collisions between ions and dust grains do not change the criteria for gravitational collapse at any value of their collision frequency, but diminish the growth rate of unstable dusty plasmas. Moreover, the rootlocus plots visualize qualitatively the evolution of the real frequencies and damping decrements of the dust-acoustic and ion-acoustic modes as the dust-ion collision frequency increases.

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PubMed2001

Dust-acoustic modes in self-gravitating plasmas with dust size distributions.

Using a kinetic description, dust-acoustic waves are considered for dusty plasmas containing, besides the electrons and ions, dust particles with continuous mass (size) distributions. For broad size spectra, self-gravitational effects cannot be neglected anymore because in the competition between electromagnetic and gravitational forces, the scale tips over towards gravitation for the heavier dust grains. Self-gravitational effects are clearly interwoven with the grain size distribution and here the effects of different power-law size distributions on the propagation, damping, and instability of low-frequency waves are discussed.

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PubMed2001

Kinetic approach to low-frequency waves in dusty self-gravitating plasmas.

A kinetic model is derived for the propagation of low-frequency waves in a dusty plasma containing very heavy dust particles, when the self-gravitational interaction due to these grains is included in the analysis. Analytical expressions for the dispersion function are used to examine the instability and damping of the modes. The stability regions of low-frequency waves are compared in the kinetic and the analogous hydrodynamic models, showing that there are only slight differences. However, the kinetic analysis modifies the growth rates of the Jeans instability and can considerably alter the conditions for the propagation of stable dust modes.

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