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Plasma Science, IEEE Transactions on

Issue 2  Part 1 • Date April 2001

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Displaying Results 1 - 25 of 33
  • Guest editorial: dusty plasmas in honor of professor d. asoka mendis on the occasion of his 65th birthday

    Page(s): 146 - 148
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  • Comments by D. Asoka Mendis

    Page(s): 151
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    First Page of the Article
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  • Investigation of a streaming instability due to dust-charge fluctuations

    Page(s): 186 - 190
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    A numerical simulation model is presented to study an important effect of dust charging on waves and instabilities in unmagnetized dusty plasmas. In this study, the background plasma is treated as a two-component fluid whose density self-consistently varies due to dust charging. The dust is treated with a particle-in-cell model in which the dust charge varies with time according to the standard dust-charging model. An ion acoustic streaming instability due to dust charging when the ion fluid drifts with respect to stationary charged dust grains and electrons is investigated. The numerical simulation results show good agreement with theoretical predictions and provide further insight into dust-charging effects on wave modes and instabilities in dusty plasmas View full abstract»

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  • Nonlinear wake potential in a dusty plasma

    Page(s): 191 - 197
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    The linear response of a dust grain to a flowing plasma has been well studied, both through analytic theory as well as by plasma simulation. The principal feature of the plasma response is a quasi-periodic wavetrain downstream of the grain, whose characteristics have been investigated as a function of the plasma conditions and grain properties. In linear theory, the magnitude of the wake potential scales as the grain charge Q. For large enough charge, one expects that nonlinear behavior will occur. Using one- and two-dimensional simulations with particle ions flowing past a fixed charged grain, we show that for sufficiently large Q, the wake potential becomes essentially independent of the grain charge. The potential is large enough to reflect some of the incident ions, which become trapped in the vicinity of the grain. Compared to our previous calculations, we also assume a larger value for the ion-neutral collision frequency, and show that the resulting wake is significantly shorter in length and steadier in time View full abstract»

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  • A dust halo of Enceladus

    Page(s): 271 - 273
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    The physical consequence of the collisional interaction of the Saturnian E-ring particles with the icy satellite Enceladus is examined. It is suggested that Enceladus should be surrounded by an extended halo of dust particles. In association with the generation of impact vapor clouds, an abundance of tiny smoke particles of 10-100 Å diameter might be created and subsequently picked up by the corotating magnetosphere. The Saturnian system could therefore be immersed in a disc of fine dust particles. The E-ring particle impact process is also important in providing a mechanism for surface mass transport and removal at Enceladus. For example, because of impact, erosion craters of diameters less than 2 km could be significantly eroded in regions where the surface age is only 100 million years old View full abstract»

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  • Nonlinear instabilities in a dusty plasma sheath

    Page(s): 198 - 201
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    The nonlinear coupling between large amplitude ion waves and dust-acoustic waves (DAWs), as well as dust-lattice waves (DLWs), in a dusty plasma sheath is considered. By employing a two-fluid approach, we derive a system of coupled equations for the ion waves and the DAWs/DLWs; the latter are nonlinearly driven by the ion wave ponderomotive force. A normal mode analysis of our nonlinearly coupled equations is performed to obtain general dispersion relations that are useful for studying modulational instabilities. The implications to laboratory plasmas are pointed out View full abstract»

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  • Fine-particle clouds controlled in a DC discharge plasma

    Page(s): 274 - 278
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    The spatial shape of fine-particle clouds in a strongly coupled state is controlled by varying a radial potential profile provided by radially segmented electrode for particle levitation and confinement under a completely DC configuration. Fine-particle clouds change their shapes from a usual two-dimensional disk to a three-dimensional cone, and finally concave cone with an increase in the radial potential slope. These profiles are closely related to an axial variation of the radial potential profile in the ion sheath above the segmented electrode. When we apply to the segmented electrode a potential profile with peaks between the radial center and edge, fine particles are rearranged to form azimuthal rings on the horizontal plane. The radial width of the rings is controlled by changing the peak width of the radial potential profile View full abstract»

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  • Interaction between a dust cloud and a magnetized plasma in relative motion

    Page(s): 302 - 306
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    The interaction between a dust cloud and a magnetized plasma is investigated by use of an idealized model where the dust particles have uniform size, a uniform density within the dust cloud, and start with the same velocity across the magnetic field in the plasma's rest frame. The interaction is found to be governed by a dimensionless parameter K which is a function of dust cloud, and ambient plasma, parameters. For K much smaller than unity, the interaction goes on for typically 1/(2πK) gyro times, with the particles in the dust cloud performing gyro motions with decreasing radius. For K close to unity, the dust motion is stopped on the order of a dust particle gyro time. For the case K≫1, the plasma in the flux tube through the dust cloud is dragged across the magnetic field over a distance of the order of Krd, where rd is the dust gyro radius, before the motion is stopped. Some expected effects for a more realistic dust cloud with density gradients, and containing dust with a spread in size, are discussed. The results have bearing on dusty plasma in space, e.g., models of the formation of spokes in Saturn's ring system View full abstract»

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  • Formation of a tripolar vortex in a contaminated electron-positron magnetoplasma with sheared flows

    Page(s): 298 - 301
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    We derive a system of nonlinear equations governing the dynamics of low-frequency electrostatic waves in a magnetized pair plasma with sheared flows that is contaminated by dust grains. For some specific profiles of the equilibrium sheared flows, the nonlinear equations admit a stationary solution in the form of a tripolar vortex. The implications of our investigation to laboratory and space plasmas are discussed View full abstract»

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  • Self-similar expansion of a nonideal dusty plasma

    Page(s): 164 - 174
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    The self-similar expansion into vacuum of a nonideal dusty plasma filling semi-infinite half space has been investigated for both unmagnetized, as well as magnetized, cases. The nonideal contributions arising from the dust species have been modeled through van der Waals' equation of state, while the electrons and the ions have been assumed to be ideal. For the unmagnetized dusty plasma, the governing equations describing the self-similar expansion have been derived and solved numerically to obtain the expansion profiles. The effect of the nonideal contributions coming from the volume reduction coefficient (because of the finite size of the dust grains) and the intergrain cohesive forces have been analyzed. It is shown that a nonideal thermal plasma expands over a much larger distance than the isothermal ideal plasma. For the magnetized case, the analysis has been carried out by using an MHD model, wherein the plasma is frozen to the the magnetic field lines, and quasi-neutrality is maintained. The expansion dynamics is described by a set of self-similar nonlinear governing equations. A parameter study of the expansion process is undertaken and the contributions of the ambient magnetic field to the expansion is discussed. Explicit analytical solutions for the case of small, but finite, amplitude perturbations for both the unmagnetized and magnetized cases have also been obtained. Here, the self-similar equations can be exactly reduced to a quadrature, thus yielding explicit analytical solutions for the plasma profiles during the expansion View full abstract»

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  • Particle simulation of dust structures in plasmas

    Page(s): 238 - 246
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    In the Earth's gravity, the dust in plasmas can form into a solid-like state In the plasma sheath. These ordered structures occur due to the balance of the interparticle forces, the gravitational force, and the sheath electric field. We have developed a particle simulation model to study the behavior of strongly coupled dust in plasmas under conditions of normal gravity and microgravity. The model includes a complete first-principles representation of the short-range strong forces of a shielded Coulomb system, as well as the long-range wake forces of a plasma with the ions streaming through the dust. The effects of charged particle scattering with neutrals and with other charges are included. Magnetic fields in the plasma may also be incorporated in the model View full abstract»

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  • Molecular dynamics simulations of plasma crystal formation including wake effects

    Page(s): 247 - 255
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    Molecular dynamics (MD) simulations are used to study dusty plasma crystal formation in three dimensions. The grain interaction model includes a spherically symmetric Debye-Huckel potential, an asymmetric wake potential, and a unidirectional external potential representing gravity and the sheath potential. We use a new form for the wake with ion-neutral collisions that reduce the interaction length of the wake. For the parameters considered, we obtain quasi-ordered structures in which the grains align into well-formed strings in the vertical direction and a more amorphous alignment of the strings themselves. Changes in the vertical alignment as a function of the wake parameters are analyzed View full abstract»

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  • Effective distribution functions for electrostatic waves in dusty plasmas with a dust-size distribution

    Page(s): 182 - 185
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    The kinetic theory for the electrostatic modes of dusty plasmas with a distribution of grain sizes is examined. It is assumed that the size distribution predominantly decreases exponentially with the mass for large sizes, and that a power law prevails for small sizes. Thermodynamic equilibrium leads to Maxwellian distributions over velocity with a fixed temperature and continuously varying mass. Smaller particles have higher thermal velocity and dominate the tail of the velocity distribution. The contribution of the dust component to the dispersion function is found to be “non-Maxwellian” and is equivalent to that for a kappa (generalized Lorentzian) distribution of monosized particles. Known results fur kappa distributions may be exploited. However, the nonlinear response of the charge density of the dust to an electrostatic potential is quite different to that of a monosized kappa distribution. In general, the definition of an effective dust distribution function for linearized electrostatic modes leads to a useful straightforward procedure to find the dispersion function. It is important to realize that the combined effects of velocity and size distribution can, in general, strongly modify the kinetic behavior of the plasma dust component View full abstract»

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  • On the rotation of a dust particulate in an ion flow in a magnetic field

    Page(s): 179 - 181
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    Spinning motion of a charged test dust particulate placed in a plasma sheath is studied. The shear of the ion flow velocity in the sheath is found to be responsible for a self-rotation of the particulate, resulting in a formation of a magnetic dipole moment. The presence of an external magnetic field will cause the spinning dust particulate to precess around the magnetic field direction, while the particulate will experience the cyclotron motion. The spinning frequency is on the order of 10 Hz, while the precession is much slower for the laboratory dust experimental conditions View full abstract»

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  • Modulational instabilities of electromagnetic waves in a collision-dominated dust-electron plasma

    Page(s): 267 - 270
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    The nonlinear coupling between large amplitude electromagnetic waves and dust-acoustic waves (DAWs) in a dust-electron plasma is considered, taking into account the combined effects of the radiation pressure and the thermal force involving the differential Joule heating of the electrons caused by the electromagnetic waves. By employing a two-fluid approach, we derive a system of coupled equations for the electromagnetic waves and the DAWs; the latter are nonlinearly driven by the radiation and thermal forces. A normal mode analysis of our nonlinearly coupled equations is performed to obtain a general dispersion relation that is useful for studying modulational instabilities. Specific results for the latter are presented in the collision-dominated regime where the electron frequency is much larger than the DAW frequency. The implications to space plasmas are pointed out View full abstract»

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  • On beam-plasma interaction in a dust-electron plasma

    Page(s): 202 - 207
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    The generation of electron plasma waves by low-energy electron beams in a dust-electron plasma, generated by UV induced photoemission or radiative heating of grains, is considered. It is shown that finite amplitude Langmuir waves might be produced due to the usual two-stream (beam-plasma) instability under certain conditions. Langmuir waves may saturate by beam trapping and attain finite amplitudes. Large amplitude Langmuir waves can nonlinearly interact with dust acoustic waves due to the parametric process. However, for the parameters considered, the rates of the decay and modulational interactions of Langmuir waves in the dust-electron plasma are much smaller than electron collisional damping rates View full abstract»

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  • The criteria for dust agglomeration in plasmas

    Page(s): 158 - 163
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    We demonstrate dust particle attraction in a plasma due to plasma particle and neutral particle bombardment. A criteria of charged dust agglomeration is found, where the attraction forces, due to bombardment, exceed the dust repulsion forces due to Coulomb interaction between like charges. Agglomerates in the systems which are optically thin for thermal radiation of dust particles is considered View full abstract»

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  • Effect of radiative cooling on molecular cloud collapse

    Page(s): 307 - 312
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    The effect of the radiative cooling of electrons on the gravitational collapse of molecular clouds consisting of neutral particles along with electrons, ions, and electrically charged dust grains with fluctuating charge is investigated. We include the effect of radiation on the gravitational collapse of the neutrals only through the ion-neutral and grain-neutral collisions. In the absence of thermal conduction, the radiative condensational instability may couple with the Jeans mode in the long-wavelength regime. However, when the thermal conduction is switched on, gravitational collapse is not altered in any significant way by the radiative mode. The charge fluctuations on the grains may slightly reduce the Jeans growth rate as the collision induced plasma electric field, which is in phase with the gravitational field, is slightly reduced by the charge variation on the grains View full abstract»

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  • Ring simulation experiment using fine-particle plasmas

    Page(s): 279 - 282
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    We can create a ring structure around a magnetized miniature sphere which is immersed in a fine-particle plasma and rotated around its magnetic dipole axis. Aluminum fine particles generated by a boat method acquire charges by UV light irradiation and are converted to a fine-particle plasma. When the magnetized sphere was rotated in the fine-particle plasma, a ring appeared around the equatorial plane under certain conditions. Unipolar induction can reveal some of ring creation mechanisms of the ring; that is, the rotation frequency matches a theoretical simulating condition, and the location of the ring almost fits with the peak position of potential, which is two to three times the sphere radius. This experiment reveals one of mechanisms why the outer planets such as the Saturn, have rings. It indicates the fact that the unipolar induction plays an important role for the creation of the outer planets in the early stage of the solar system formation View full abstract»

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  • A new electromagnetic wave in a dust-ion plasma

    Page(s): 208 - 209
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    It is shown that a magnetized dust-ion plasma can support a new low-frequency circularly polarized dispersive electromagnetic wave, whose frequency is proportional to the wave electric field amplitude. In the new wave, inertia comes from the dust mass, whereas the restoring force is associated with the medium polarization due to relativistic ion motion. The implication of our investigation to cosmic plasmas is pointed out View full abstract»

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  • Formation of liquidlike and crystalline structures in dusty plasmas

    Page(s): 210 - 215
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    A study of the strongly coupled dusty plasma was carried out over a wide range of plasma pressures and temperatures. The plasma was investigated under conditions of low-pressure inductively coupled radio frequency gas discharge and under thermal plasma conditions at atmospheric pressure. The plasma was also formed from positively charged dust grains in the presence of a flux of ultraviolet photons. The results of experimental observations of ordered dust structures are reported, and the characteristic features of the dust structures and the conditions for their appearance are discussed View full abstract»

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  • Computer simulations of Coulomb crystallization in a dusty plasma

    Page(s): 231 - 237
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    It has been shown experimentally that under the proper conditions, a dusty plasma system can form an ordered, crystalline state known as a Coulomb or dust crystal. This paper uses a computer simulation to model the behavior of such a system while several parameters are changed independently of one another, something that is experimentally difficult to do. The computer program used is a modified Barnes-Hut tree code known as “Box Tree.” Tree codes allow all of the interparticle interactions to be calculated including the medium- and long-range interactions created by distant particles using multipole expansions. The simulation is also used to explore the possibility that the end state of the system may depend (at least in part) on its past history (whether it is initially in a solid or disordered state), or the evolution of κ and Γ themselves. As expected, it is shown that as the coupling parameter increases the amount of order present within a system also increases. Unexpectedly, the simulation also shows that the amount of order present within a dusty plasma system is not necessarily completely determined by Γs and κ View full abstract»

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  • Ion field emission from micrometer-sized spherical glass grains

    Page(s): 292 - 297
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    An experimental investigation of ion field emission from spherical glass grains in a 1-10 μm size range is described. A single dust grain is trapped in an electrodynamic quadrupole and charged positively by a monoenergetic ion beam. The energy of these ions (5 keV) results in a high surface potential and high electric field intensity. A limitation of the surface potential due to ion field emission was observed for the surface field intensity of 3×108 V/m, which is a considerably lower value than expected. The density of the discharging current was as high as 10-5 A/m2, and increased exponentially with increasing intensity of the electric field. As there are no data of the ion field emission from insulators, we have used the zinc grains for a comparison. Taking into account the irregular shape of used metallic grains, we conclude that the ion field emission from the glass grains starts at a significantly (two orders of magnitude) lower electric field intensity than that from metals. This may lead to the limitation of the attainable surface potential of small insulator grains. The possible effect of the ion field emission on the charging of dust grains in the interplanetary space is discussed View full abstract»

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  • On equilibrium states and dust charging in dusty plasmas

    Page(s): 175 - 178
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    The dust-charge variation process is revisited, accounting for the background density variation associated with electron capture and release by the dust grains. It appears possible to maintain overall charge neutrality in the plasma without any external particle source or sink. It is shown that if the dust charge and density are sufficiently high, the effect of the background electron density variation on dust-charge relaxation is important. The equilibrium dust charge and its rate of variation are obtained for dusty plasmas subject to strong UV irradiation. The latter releases photoelectrons from the dust surface and can significantly affect the equilibrium dust charge, its variation rate, as well as the overall charge neutrality in the plasma View full abstract»

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Aims & Scope

IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

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Editor-in-Chief
Steven J. Gitomer, Ph.D.
Senior Scientist, US Civilian Research & Development Foundation
Guest Scientist, Los Alamos National Laboratory
1428 Miracerros Loop South
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