摘要:

During the last decade, we have seen a very rapid growth of the dusty plasma physics with many discoveries. The latter include the dust acoustic wave, the wakefield and the ion focusing (which are responsible for the attraction of charged dust grains), the dusty plasma crystals as well as coherent nonlinear structures comprising the dust ion-acoustic shocks, the dust acoustic Mach cones, voids, and vortices. Since the dusty plasma physics involves the charging and the dynamics of extremely massive charged dust grains, it can be characterized as a complex plasma system whose characteristics are significantly different from the usual multi-ion plasmas. In this paper, we present the properties of a complex dusty plasma, as well as discuss two novel instabilities that are responsible for the excitation of low-frequency electrostatic modes in an unmagnetized dusty plasmas. The instabilities are associated with the combined effects of a dc electric field and the dust charge gradient on one hand, and the rotation of elongated dust grains on the other hand. The implications of the present investigation to laboratory and space plasmas are discussed. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1324917

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The propagation of ultra low-frequency electrostatic modes in dusty plasmas has been reviewed in the light of the concept of dust fugacity (f&hthinsp;), which is defined byf≡4&pgr;nd0&lgr;D2Rwherend0,&lgr;DandRare, respectively, the dust number density, the plasma Debye length and the grain size (radius). Dusty plasmas are defined to be tenuous, dilute or dense according asf≪1,∼1, or ≫1, respectively. By using the fluid as well as the kinetic (Vlasov) theories, attention is focused on the “Dust-Acoustic Waves” (DAWs) and the “Dust-Coulomb Waves” (DCWs) which exist in the tenuous and the dense regimes, respectively. Unlike the DAWs which exist even for constant grain charge, the DCWs are thenormal modesassociated with grain charge fluctuations, and are driven by an effective pressure called “Coulomb Pressure”. They can be considered as the electrostatic analogue of the hydromagnetic (Alfve´n or magnetoacoustic) modes which are driven by the magnetic field pressure. In the dilute regime, the two modes merge into a single mode, which may be called the “Dust Charge-Density Wave” (DCDW). When the grains are closest, the DCW dispersion relation is identical with that of the “Dust-Lattice Waves” (DLWs). Dense dusty plasmas are shown to be governed by anew scale-lengthdefined by&lgr;R≡1/4&pgr;nd0R&dgr;,where &dgr; is a parameter related to the charging frequencies. The scale-length&lgr;Rcharacterizes the effective shielding length due to the collective grain interactions, and plays a fundamental role in dense dusty plasmas, which is very similar to that of the Debye length(&lgr;D)of the tenuous regime. The frequency spectrum as well as the damping rates for the various dust modes have been analytically obtained, and compared with the numerical results. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1324918

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Charged dust grains can have a large effect on the dispersion characteristics of hydromagnetic Alfve´n and magnetoacoustic waves propagating at frequencies well below the ion-cyclotron frequency, even if the proportion of the total charge on the dust (usually negative) is quite small in space and astrophysical plasmas, such as cometary atmospheres and interstellar molecular clouds. The dust introduces a cutoff-resonance pair. A number of effects of the dust are considered here. Wave energy propagating at oblique angles to the magnetic field in an increasing density gradient can be very efficiently damped by resonance absorption processes in a dusty plasma. It is shown that, as well as the usual Alfve´n resonance, a low frequency dust-ion hybrid resonance also occurs. The effects of dust on the dispersion of surface waves in highly structured plasmas and damping due to dust charging may also play roles in such plasmas. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1324919

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The self-similar expansion of a warm non-ideal magnetized dusty plasma filling semi-infinite half space has been investigated by incorporating the van der Waals equation of state for the dust species. The analysis has been carried out by using an MHD model wherein the plasma is frozen to the magnetic field lines and quasi charge-neutrality is maintained. The expansion dynamics is described by a self-similar set of nonlinear equations, which are numerically solved for the dust density, velocity and pressure profiles. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1324920

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

An analysis of low-frequency modes accounting for dust grain charge fluctuation and equilibrium grain charge inhomogeneity in a strongly coupled dusty plasma is presented. The existence of an extremely low frequency mode, which is due to the inhomogeneity in the equilibrium dust grain charge, is reported. Besides, the equilibrium dust grain charge inhomogeneity makes the dust-acoustic mode unstable. The strong correlations in the dust fluid significantly drive a new mode as well as the existing dust-acoustic mode. The applications of these results to recent experimental and to some space and astrophysical situations are discussed. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1324921

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A TMA (tri-methyl aluminum) release rocket launched during the 1998 Coqui II sounding rocket campaign in Puerto Rico produced what appeared to be an artificially-generated aurora. This phenomenon has been observed on several other occasions, but has not yet been fully investigated. Charged particulates in the TMA trail may excite plasma or dusty plasma instabilities resulting in particle acceleration and auroral-like atmospheric emissions. We discuss several possible scenarios here, though determination of the appropriate particle acceleration mechanism will only be possible after more experimental and theoretical work. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1324922

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Self-gravitational modes in dusty plasmas have been extensively studied for both extreme cases of wave propagation: waves propagating parallel to an external magnetic field and perpendicularly propagating waves. Provided the presence of neutral is insignificant, the presence of charged dust species stabilizes plasmas against gravitational collapse, the mechanisms being induced by plasma thermal effects and/or magnetic field pressure. We present here the modifications of magnetosonic modes and electrostatic, parallel modes due to the possible distributions of the dust mass. The necessary adaptations of the corresponding critical Jeans lengths are discussed and extended to intermediate angles of propagation. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1324923

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Using a kinetic approach, a parametric investigation of electrostatic instabilities is undertaken in a two-dust component plasma comprising of ions, electrons and two dust species (of different mass and charge) in the low dust plasma frequency regime. These instabilities are driven by an equalE×Bdrift of the ions and electrons relative to the stationary, unmagnetized dust grains. The effects of the variation of plasma parameters such as particle drift speeds, densities and temperature on the instability real frequency and growth rate are examined. Numerical solutions of the full dispersion relation are compared with approximate solutions. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1324924

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The linear as well as the nonlinear propagation of dust-acoustic waves (DAWs) in non-ideal dusty plasmas comprising of electrons, ions and dust grains has been studied by self-consistently including the grain charge variations. The non-ideal effects are incorporated through the van der Waals equation of state for the dust fluid, while the charge fluctuation effects come in through the current balance equation. The real frequency and the damping rate for the linear DAWs are investigated and the reductive perturbation approach has been used to derive a K-dV-like equation governing the nonlinear evolution of the DAWs. The combined effects of the non-ideal contributions and the grain charge fluctuations in the linear as well as the nonlinear regimes of wave propagation are discussed. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1324925

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

In this paper the foundation is layed for the nonmodal investigation of velocity shear induced phenomena in a differentially rotating flow of a dusty plasma. The simplest case of nonmagnetized flow is considered. It is shown that, together with the innate properties of the dusty plasma, the presence of differential rotation, Coriolis forces, and self-gravity casts a considerable richness on the nonmodal dynamics of linear perturbations in the flow. In particular: (i) dust-acoustic waves acquire the ability to extract energy from the mean flow and (ii) shear-induced, nonperiodic modes of collective plasma behavior—shear-dust-acoustic vortices—are generated. The presence of self-gravity and the nonzero Coriolis parameter (“epicyclic shaking”) makes these collective modes transiently unstable. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1324926

出版商:AIP    

年代:1900

数据来源: AIP