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Nonplanar Shocks and Solitons in a Strongly Coupled Adiabatic Plasma: the Roles of Heavy Ion Dynamics and Nonextensitivity

An investigation has been made on heavy ion-acoustic (HIA) nonplanar shocks and solitons in an unmagnetized, collisionless, strongly coupled plasma whose constituents are strongly correlated adiabatic inertial heavy ions, weakly correlated nonextensive distributed electrons and Maxwellian light ions. By using appropriate nonlinear equations for our strongly coupled plasma system and the well-known reductive perturbation technique, a modified Burgers (mB) equation and a modified Korteweg-de Vries (mK-dV) equation have been derived. They are also numerically solved in order to investigate the basic features (viz. polarity, amplitude, width, etc.) of cylindrical and spherical shock/solitary waves in such a strongly coupled plasma system. The roles of heavy ion dynamics, nonextensivity of electrons, and other plasma parameters arised in this investigation have significantly modified the basic features of the cylindrical and spherical HIA solitary and shock waves. The findings of our results obtained from this theoretical investigation may be useful in understanding the nonlinear phenomena associated with the cylindrical and spherical HIA waves both in space and laboratory plasmas. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Jeans instability of a dusty plasma with dust charge variations

The effect of the dust charge variations on the stability of a self-gravitating dusty plasma has been theoretically investigated. The dispersion relation for the dust-acoustic waves in a self-gravitating dusty plasma is obtained. It is shown that the dust charge variations have significant effects. It increases the growth rate of instability and the instability cutoff wavenumbers. It is found that by increasing the value of the ions temperature and the absolute value of the equilibrium dust charge, the cutoff wavenumber decreases and the stability region is extended.

Oblique collision of dust acoustic solitons in a strongly coupled dusty plasma

The oblique collision between two equal amplitude dust acoustic solitons is observed in a strongly coupled dusty plasma. The solitons are subjected to oblique interaction at different colliding angles. We observe a resonance structure during oblique collision at a critical colliding angle which is described by the idea of three wave resonance interaction modeled by Kadomtsev-Petviashvili equation. After collision, the solitons preserve their identity. The amplitude of the resultant wave formed during interaction is measured for different collision angles as well as for different colliding soliton amplitudes. At resonance, the maximum amplitude of the new soliton formed is nearly 3.7 times the initial soliton amplitude.

Polarization force-induced changes in the dust sheath formation

The modifications arising in the dusty plasma sheath structure due to the presence of polarization forces acting on the dust grains are investigated. The corresponding appropriate Bohm criterion for sheath formation is obtained. It is found that the critical Mach number, beyond which the dusty plasma electrostatic sheath sets in, decreases whenever the polarization effects become important. In addition, when the polarization force dominates over the electrical one, the dust plasma sheath cannot set in. This happens whenever the dust grain size exceeds a critical threshold. Moreover, the sheath electrostatic potential-gradient becomes abruptly steep, and the sheath thickness becomes broader as the polarization force effects strengthen.

Multidimensional Instability of Dust-Acoustic Solitary Waves in a Magnetized Hot Dusty Plasma with Superthermal Electrons and Ions

Multidimensional instability of dust-acoustic solitary wave (DASW) in magnetized dusty plasma with superthermal electrons and ions and micron size hot dust particles is investigated. The Zakharov-Kuznetsov (ZK) equation, describing the small but finite amplitude DASW, was derived using the reductive perturbation method and its solitary answers was introduced. Effects of electrons and ions superthermality as well as the external magnetic field on the nature of DASW are discussed in detail. Dispersion relation, threshold condition, and growth rate of multidimensional instability of DASW were derived using small-k (long wavelength plane wave) perturbation expansion method. We found that the direction and strength of external magnetic field extremely affect the growth rate and instability criterion. Results show that growth rate of instability decreases with increasing the number of superthermal electrons and increases with increasing the number of superthermal ions. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Kinetic energy in a system of particles with a nonreciprocal interaction

We present a theoretical model for the description of the heating mechanism and the redistribution of kinetic energy in a system of particles with nonreciprocal interactions that occur in disperse systems of different nature. To verify the theory, we carried out the numerical simulations of two-particle systems with a nonreciprocal “quasi-dipole–dipole” interaction that is similar to the interaction due to the effect of ion focusing in a laboratory complex plasma under experimental conditions. The proposed model of heating can explain various features of dust dynamics in anisotropic complex plasma.

Thermionic and photoelectric emission of electrons from positively charged particles in a plasma with Debye shielding

By utilizing the recent concept [G. Delzanno et al., Phys. Plasmas 12, 062102 (2005) and G. Delzanno and X. Tang, Phys. Rev. Lett. 113, 035002 (2014)] that the radial potential, experienced by an electron in the vicinity of a positively charged spherical particle depends on the transverse momentum of the electron, we have evaluated the rate of thermionic and photoelectron emission from a positively charged spherical particle and the corresponding average electron energy in a plasma, with Debye Screening. The effect of screening is manifested in the magnitude of a maximum in the radial potential energy versus r curve and is characterized by a parameter β which depends solely on ( r 0 / λ ) . Simple expressions for the change in the rates of emission and corresponding electron energy due to inclusion of the mechanism (mentioned above) in the analysis have been derived. The results of numerical computations have been presented and discussed. Simple expressions for the rates of electron emission from positively charged particles and corresponding average electron energy are necessary in the study of kinetics of complex plasmas. This work suffers from the limitation that the Debye length and even the nature of screening is not apriori known. In general, the evaluation of the nature of shielding and the shielding length requires a self consistent computation, similar to that carried out by Delzanno and Tang [Phys. Rev. Lett. 113, 035002 (2014)] in their work on thermionic emission in vacuum.

Viscosity of confined two-dimensional Yukawa liquids: A nonequilibrium method

We present a nonequilibrium method that allows one to determine the viscosity of two-dimensional dust clusters in an isotropic confinement. By applying a tangential external force to the outer parts of the cluster (e.g., with lasers), a sheared velocity profile is created. The decay of the angular velocity towards the center of the confinement potential is determined by a balance between internal (viscosity) and external friction (neutral gas damping). The viscosity can then be calculated from a fit of the measured velocity profile to a solution of the Navier-Stokes equation. Langevin dynamics simulations are used to demonstrate the feasibility of the method. We find good agreement of the measured viscosity with previous results for macroscopic Yukawa plasmas.

Linear and nonlinear heavy ion-acoustic waves in a strongly coupled plasma

A theoretical study on the propagation of linear and nonlinear heavy ion-acoustic (HIA) waves in an unmagnetized, collisionless, strongly coupled plasma system has been carried out. The plasma system is assumed to contain adiabatic positively charged inertial heavy ion fluids, nonextensive distributed electrons, and Maxwellian light ions. The normal mode analysis is used to study the linear behaviour. On the other hand, the well-known reductive perturbation technique is used to derive the nonlinear dynamical equations, namely, Burgers equation and Korteweg-de Vries (K-dV) equation. They are also numerically analyzed in order to investigate the basic features of shock and solitary waves. The adiabatic effects on the HIA shock and solitary waves propagating in such a strongly coupled plasma are taken into account. It has been observed that the roles of the adiabatic positively charged heavy ions, nonextensivity of electrons, and other plasma parameters arised in this investigation have significantly modified the basic features (viz., polarity, amplitude, width, etc.) of the HIA solitary/shock waves. The findings of our results obtained from this theoretical investigation may be useful in understanding the linear as well as nonlinear phenomena associated with the HIA waves both in space and laboratory plasmas.

Electron energy distribution in a dusty plasma: Analytical approach

Author(s): I. B. Denysenko, H. Kersten, and N. A. Azarenkov

Analytical expressions describing the electron energy distribution function (EEDF) in a dusty plasma are obtained from the homogeneous Boltzmann equation for electrons. The expressions are derived neglecting electron-electron collisions, as well as transformation of high-energy electrons into low-en…


[Phys. Rev. E 92, 033102] Published Tue Sep 08, 2015