Presence Of Dust Charge Fluctuation Research Articles

Kinetic theory of effect of dust charge fluctuations on the parametric decay of lower hybrid wave instability by relativistic runaway electrons in tokamak

Dust charge fluctuation effect on the parametric decay of lower hybrid wave instability by relativistic runaway electrons is studied in a tokamak using kinetic treatment. Parametric upconversion of lower hybrid pump waves into relativistic runaway electron mode and upper sideband mode is described. A ponderomotive force is exerted on the runaway electrons by lower hybrid pump wave possessing large amplitude and upper sideband wave, which drives the runaway electron mode. The coupling of the oscillatory velocity of electrons with density perturbations produces nonlinear density perturbations on the upper sideband frequency. As a result, runaway generation is enhanced by a lower hybrid wave and the growth rate of the instability is measured as the square of the amplitude of the pump wave. Moreover, the presence of dust charge fluctuations and their number density in the tokamak have an appreciable effect on the growth rate of lower hybrid wave instabilities, which in turn affects the actual performance of the ITER due to the potential safety and operational issues.

Dust-ion-acoustic shock waves in the presence of dust charge fluctuation in non-Maxwellian plasmas with Kappa-distributed electrons

A three-component plasma composed of nonthermal Kappa-distributed electrons, mobile ions, stationary and dust-fluctuating (spherical) dust particles is considered. By employing reductive perturbation method in a weakly nonlinear limit, the Burger’s equation has been derived and the basic properties of dust ion acoustic shock waves are analyzed. It is observed that for increasing ion–electron temperature ratio, the shock’s amplitude decreases, and vice versa. Moreover, shock steepens for increasing electron–ion equilibrium density ratio. Furthermore, it is observed that the shock potential distribution is directly proportional to the spectral index κ, whereas the shock’s width is inversely proportional to the latter. Thus, the non-Maxwellian nature of the electronic velocity distribution significantly modifies the perturbed potential profile. In the limiting case κ→∞, the corresponding Maxwellian results are retrieved. Present work will be useful in understanding the nonlinear propagation of dust-ion-acoustic shock waves (DIASHW) in space plasmas where nonthermal population of electrons exist due to various physical phenomena, and in laboratory (e.g., in a double plasma (DP) device, or in tokamak where runaway electrons may result in a non-Maxwellian plasma).

Modified Jeans instability of collisional dusty magnetoplasma in presence of radiative cooling and dust charge fluctuation

We have investigated the modifications in the self-gravitational instability of magnetized collisional dusty plasma, arising from the radiative effects of electrons and ions, and charge fluctuation of dust. The electron and ion dynamics are described by their radiative effects and considering the full dynamics of dust and neutrals, the general dispersion relation is derived. The properties of the general dispersion relation are discussed in the absence and presence of dust charge fluctuation. The results of these two cases are further reduced for parallel and perpendicular modes of propagation. The consequences of magnetic field, collisions, dust charge fluctuation, and radiative condensation on the growth rate of self-gravitational instability are discussed analytically and graphically. We found that the radiative effects and dust charge variation increase the growth rate of self-gravitational instability while the presence of magnetic field and collisions shows the stabilizing behavior. The findings are discussed in context of the structure formation in interstellar clouds.

Propagation of dust acoustic solitary waves in inhomogeneous plasma with dust charge fluctuations

Propagations of dust acoustic solitary waves are theoretically investigated in a collisionless, unmagnetized weakly inhomogeneous plasma. The plasma that is considered here consists of negatively charged dust grains and Boltzmann distributed electrons and ions in the presence of dust charge fluctuations. The fluid equations that we use for description of such plasmas are reduced to a modified Korteweg–de-Vries equation by employing a reductive perturbation method. In this investigation, we have used space–time stretched coordinates appropriate for the inhomogeneous plasmas. From the numerical results, we have observed a significant influence of inhomogeneity parameters on the propagation of dust acoustic solitary waves.

The linear and non-linear characterization of dust ion acoustic mode in complex plasma in presence of dynamical charging of dust

A systematic theoretical investigation has been carried out on the role of dust charging dynamics on the nature and stability of DIA (Dust Ion Acoustic) mode in complex plasma. The study has been made for both linear and non-linear scale regime of DIA mode. The observed results have been characterized in terms of background plasma responses towards dust surface responsible for dust charge fluctuation, invoking important dusty plasma parameters, especially the ion flow speed and dust size. The linear analyses confirm the nature of instability in DIA mode in presence of dust charge fluctuation. The instability shows a damping of DIA mode in subsonic flow regime followed by a gradual growth in instability in supersonic limit of ion flow. The strength of non-linearity and their existence domain is found to be driven by different dusty plasma parameters. As dust is ubiquitous in interstellar medium with plasma background, the study also addresses the possible effect of dust charging dynamics in gravito-electrostatic characterization and the stability of dust molecular clouds especially in proto-planetary disc. The observations are influential and interesting towards the understanding of dust settling mechanism and formation of dust environments in different regions in space.

DEA Waves With Cold and Hot Electrons

The theoretical and numerical studies have been made to observe the planar and nonplanar geometries for the nonlinear propagation of the dust-electron-acoustic (DEA) in a dusty plasma (containing initially cold and hot Maxwellian electrons, stationary ions, and charge fluctuating stationary dust grains) using reductive perturbation method. It has also been found that the basic features of the DEA waves are significantly modified by the presence of dust charge fluctuation. The numerical solution to the K-dV equation indicates that the parameters those we have considered in our model blatantly influence the propagation speed and the structure of DEA solitary waves. The geometrical effects on the structure of DEA wave are discussed. It is shown that the amplitude and propagation speed in spherical geometry is larger compared with cylindrical and planar geometries for different values of the above-mentioned parameters. The implications of our results would be useful to understand some astrophysical and cosmological scenarios like stellar polytropes, hadronic matter and quark-gluon plasma, protoneutron stars, and dark-matter halos.

Dust Acoustic Shock Waves with Non-Thermal and Vortex-Like Ions in Dusty Plasma

A rigorous investigation is presented on the propagation characteristics of non-linear dust acoustic (DA) waves in an unmagnetized dusty plasma system containing non-thermal and vortex-like ions and Maxwellian electrons under the effect of a fluctuating charged dust fluid. The three-dimensional (3D) Burgers' equation and a new form of a lower degree modified 3D Burgers' equation with their analytical solutions are derived to study the features of shock waves in such plasmas. The effect of the population of non-thermal ions, the vortex-like ion parameter as well as the temperature ratios of ions and electrons on the evolution of shock waves in the presence of dust charge fluctuation is presented. This theoretical investigation might be effectively utilized to unveil the nature of many astrophysical plasma environments (Saturn's spokes etc.) where such plasmas are reported to have existed.

Decay instability of an upper hybrid wave in a magnetized dusty plasmas

The decay instability of an upper hybrid wave into an upper hybrid sideband wave and low frequency ion-cyclotron wave are studied in a magnetized dusty plasma cylinder. The growth rate and ion-cyclotron mode frequencies were evaluated based on existing dusty plasma parameters. It is found that the unstable mode frequency increases linearly with δ (ion-to-electron density ratio). In addition, the growth rate of the unstable ion-cyclotron mode decreases sharply for lower values of δ in the presence of dust charge fluctuations, i.e., the dust grains increases the damping effect in three wave interaction process.

Cosmic dust-laden plasma expansion: the role of charged impurities

The ionization source model is considered to study the expansion of a cosmic dust-laden plasma. Source and sink terms are included in fluid equations to investigate the one-dimensional self-similar expansion in the presence of dust charge fluctuation. As a consequence of the presence of neutralizing heavy particles and momentum transfer, the validity domain of the self-similar solution is found to increase with dust initial charge. The ion density profile is also found to depend on the dust charge value.

Electrostatic ion-temperature-gradient drift-waves and anomalous energy transport in a collisional dusty magnetoplasma

Electrostatic ion-temperature-gradient (ITG) driven drift waves are investigated by using Brangskii's model for the ions and Boltzmann distribution for the electrons in a dust-contaminated plasma with equilibrium density, temperature, and magnetic field gradients. Within the local approximation, we are able to recover the coupled ion-acoustic drift-waves in an inhomogeneous magnetic field and the Rudakov–Sagdeev (R–S) ITG instability in the presence of dust-charge fluctuations. It has been shown that the dust charging is always dissipative and the growth rate of various modes are damped. Furthermore, we also derive an expression for the anomalous ion-energy flux and transport coefficient in the presence of nonthermal fluctuations. The present investigation should be helpful in identifying the features of low-frequency turbulence and associated cross-field ion-energy transport in magnetically confined dust-contaminated tokamak plasmas.

Nonlinear dynamics of electrostatic ion-temperature-gradient modes in a dust-contaminated plasma with variable charge and sheared ion flows

By employing Braginskii transport equations for ions and Boltzmann distribution for electrons in a dust-contaminated plasma with equilibrium density, temperature, and magnetic field gradients, the nonlinear set of equations are derived. New ion-temperature-gradient driven modes are obtained and various limiting cases are discussed. It is shown that the ion-temperature-gradient driven mode of drift-waves are attenuated in the presence of dust-charge fluctuations. It has been found that dust charging is always dissipative and the growth rate of various modes are damped. Furthermore, the possible stationary solution of the nonlinear mode coupling equations can be represented in the form of dipolar and vortex chains type solutions. The results of the present investigation should be helpful in understanding the fluctuations and transport phenomena in magnetically confined dustcontaminated tokamak plasma.

Dust-lower-hybrid instability in the presence of dust charge fluctuations in a magnetized dusty plasma

The growth and damping of the low-frequency electrostatic dust-lower-hybrid (DLH) wave have been examined in the presence of dust charge fluctuations in a uniform magnetized dusty plasma. To obtain the dust charge fluctuation effects, the charging currents of electrons and ions to a spherical dust grain in a uniform magnetized dusty plasma have been calculated under the orbit-limited motion approximation. It is found that the external magnetic field reduces the charging currents, thereby reducing the dust charge fluctuation damping of a low-frequency electrostatic wave in a dusty plasma. However, for sufficiently low-frequency DLH wave having a finite parallel wave number, the thermal electrons may give rise to an instability of the DLH wave.

Thermal condensation mode in a dusty plasma

In the present work, the radiative condensation instability is investigated in the presence of dust charge fluctuations. We find that the charge variability of the grain reduces the growth rate of radiative mode only for fluctuation wavelength smaller or of the order of the Debye length and this reduction is not very large. Far from the Debye sphere, radiative mode can damp due to thermal conduction of electrons and ions

Dust-lower-hybrid instability in the presence of dust charge fluctuation in a streaming dusty plasma

A detailed theoretical investigation has been made on the properties and excitation of low-frequency and low-phase-velocity electrostatic dust-modes in a magnetized dusty plasma including the streaming of ions, dust charge fluctuation, and the kinetic effects using the Vlasov–Poisson analysis. In the case of high-density dusty plasma, the dust-lower-hybrid (dlh) mode propagating nearly transverse to the external static magnetic field is obtained. On the other hand, for the low-density dusty plasma, the dust-acoustic (DA) wave propagating nearly perpendicular to the external magnetic field has been obtained. It is found that in any case of the above dust-modes, the Landau damping linearly adds to the damping due to dust charge fluctuation. These low-frequency modes can be excited when the ion streaming velocity exceeds the parallel phase velocity of the mode provided the damping due to the dust charge fluctuation is smaller than the Landau damping term of the respective mode. Moreover, it is found that the DA mode is damped rapidly compared to the dlh-mode through charge fluctuation and Landau damping processes.

The Pulsational Mode in the Presence of Dust Charge Fluctuations

The pulsational mode of gravitational collapse of a dusty plasma is studied in the present work. We find that the grain charge fluctuation defines a parameter regime in which pulsational mode of gravitational collapse (PMGC), which is a consequence of the gravito-electrostatic coupling, is permitted, and outside such a parameter regime, usual Jeans mode ensues. Therefore, grain charge fluctuations may play an important role in deciding which of the two modes, namely PMGC or usual Jeans instability of a collapsing cloud will be important. We find that the growth rate of Jeans instability is not very sensitive to the grain charge fluctuations.

Effect of dust charge fluctuation on the Alfvén wave propagation in a magnetized dusty plasma

Growth rates of propagating waves in a magnetized dusty plasma are studied for various values of natural decay rate for the presence of dust charge fluctuation in the case of hot ions and electrons and for a weak magnetic field. The dispersion relation is obtained for the waves that propagate through low-frequency plasma with velocity, VA=B0/(μominio)1/2. Consistency of the results with previous work [Alam et al., Astrophys. Space Sci. 259, 15 (1998)] is discussed and the physical situation is also seen to be the situation considered in Varma et al. [Phys. Rev. E 47, 3612 (1993)] and Melandsø et al. [Planet Space Sci. 41, 321 (1993)]. At last, numerical estimates of the growth rate as a function of the attachment frequency, the decay rate for its various range of values have been done and are displayed graphically.

Coherent structures in presence of dust charge fluctuations

This paper shows the formation of nonlinear coherent structures in a dusty plasma in presence of dust charge fluctuations. Using the typical plasma parameters the potential of the nonlinear coherent structures is derived.

The Kelvin–Helmholtz instability in the presence of dust charge fluctuations

Kelvin–Helmholtz instability is examined by considering the dust charge fluctuations in a dusty plasma. Electrons and ions are assumed to be in Boltzmann equilibria and the dust grains to follow the fluid equations with a full adiabatic equation of state. The transverse shear in the flow parallel to the magnetic field is considered. The instability is found to grow for limiting wave numbers for a particular value of shear velocity. The effect of adiabatic dust plasma pressure is to enhance the growth rate of the instability. For dense plasma, growth of the instability is affected by the presence of dust charge fluctuations.

Dust cyclotron instability in presence of dust charge fluctuations

Electrostatic ion cyclotron instability has been studied in presence of dust charge fluctuation. A comparative study has been done between instability in absence of dust charge fluctuation and in presence of that. It is observed that the critical velocity of electrons for the onset of instability increases due to dust charge fluctuations.

Propagation of a small-amplitude shock wave associated with the ion acoustic-like mode in a dusty plasma

The reductive perturbation method is used to investigate the existence of a shock wave in the presence of dust charge fluctuation in a dusty plasma. A Burgers-type equation is obtained for the first-order perturbed potential. The potential and velocity of the shock are obtained. The conditions for the existence of the shock solutions are discussed.