M. Asaduzzaman

Dust-acoustic Gardner solitons and double layers in dusty plasmas with nonthermally distributed ions of two distinct temperatures.

A rigorous theoretical investigation has been performed on dust-acoustic (DA) solitary structures in an unmagnetized dusty plasma, consisting of negatively charged mobile dust grains, Boltzmann distributed electrons, and nonthermally distributed ions of two distinct temperatures. The Korteweg-de Vries (K-dV), modified K-dV (mK-dV) and Gardner equations, and their solitary waves (SWs) and double layer (DL) (in case of Gardner equation) solutions are derived by using the reductive perturbation technique. The basic features of the DA Gardner solitons (GSs) and DLs are studied analytically as well as numerically. It has been observed that the GSs significantly differ from K-dV and mK-dV solitons, and only positive potential DLs exist in the system. It is also studied that two-temperature nonthermal ions significantly modify the nature and basic properties of the DA SWs. The present investigation can be very effective for understanding and studying the nonlinear characteristics of the DA waves in laboratory and space dusty plasmas.

Dust-ion-acoustic Gardner solitons in a dusty plasma with bi-Maxwellian electrons

The nonlinear propagation of dust-ion-acoustic (DIA) waves in a dusty plasma with bi-Maxwellian electrons, namely, lower and higher temperature electrons (composed of negatively charged stationary dust, inertial ions, and non-inertial two-temperature-electrons) is investigated by deriving the Gardner equation using the reductive perturbation technique. The basic features (amplitude, width, etc.) of the hump (positive potential) and dip (negative potential) shaped DIA solitons (Gardner solitons, i.e., GSs) are found to exist beyond the Korteweg-de Vries (K-dV) limit. These DIA-GSs are qualitatively different from the K-dV and modified K-dV solitons. It is also shown that depending on the parameter σ (where σ=Te1/Te2, Te1 and Te2 being the temperatures of two distinct electrons and Te1≪Te2), the DIA-GSs exhibit hump and dip shape solitary structures. The implications of our results in understanding the localized nonlinear electrostatic perturbations observed in double-plasma machines, rf discharge plasma, n...

Dust-acoustic waves in nonuniform dusty plasma in presence of polarization force

The effects of the dust density nonuniformity and the polarization force on linear propagation of the dust-acoustic waves in a nonuniform dusty plasma (consisting of electrons, ions, and arbitrarily charged dust particles) have been theoretically investigated. It has been shown that the linear dispersion properties of the dust-acoustic (DA) waves have been significantly modified by the dust density nonuniformity, dust polarity, and the polarization force. It is also found here that the phase speed of the DA waves is decreased by the effects of polarization force, and that their amplitude increases with the decrease of equilibrium dust number density. The different situations, which are relevant to different space and laboratory dusty plasmas, have been briefly discussed.

Evolution of higher order nonlinear equation for the dust ion-acoustic waves in nonextensive plasma

There are three different types of nonlinear equations, namely, Korteweg-de Vries (K-dV), modified K-dV (mK-dV), and mixed modified K-dV (mixed mK-dV) equations, for the nonlinear propagation of the dust ion-acoustic (DIA) waves. The effects of electron nonextensivity on DIA solitary waves propagating in a dusty plasma (containing negatively charged stationary dust, inertial ions, and nonextensive q distributed electrons) are examined by solving these nonlinear equations. The basic features of mixed mK-dV (higher order nonlinear equation) solitons are found to exist beyond the K-dV limit. The properties of mK-dV solitons are compared with those of mixed mK-dV solitons. It is found that both positive and negative solitons are obtained depending on the q (nonextensive parameter).

Roles of polarization force and nonthermal electron on dust-acoustic waves in an inhomogeneous dusty plasma with positively charged dust

The influence of polarization force (PF) (arises due to dust density inhomogeneity), nonthermal electrons, and dust density inhomogeneity associated with positively charged dust on linear dust-acoustic (DA) waves in an inhomogeneous unmagnetized dusty plasma are investigated. By taking the normal mode analysis, the dispersion relation in such a non-Maxwellian inhomogeneous plasma is obtained, and that the dispersion properties of the DA waves are significantly modified by the presence of PF and nonthermal electrons. The PF is increased with the increase of nonthermal electrons. It is found that the phase speed of the DA waves is significantly decreased with the presence of PF and nonthermal electrons. The potential associated with the DA waves is de-enhanced with the increase of equilibrium dust number density. The role of positive dust number density on dispersion properties is also shown. The present findings relevant to different scenarios in laboratory and space dusty plasma, such as Martian ionospher...

Effects of polarization force and fast electrons on DA shock waves in a strongly coupled dusty plasma

A strongly coupled dusty plasma system consisting of non-thermal electrons, Maxwellian ions, and negatively charged dust in presence of polarization force has been considered. The nonlinear propagation of dust-acoustic shock waves in such a dusty plasma system has been theoretically investigated by employing the reductive perturbation method. The effects of the polarization force and non-thermal electrons, on the properties of these dust-acoustic shock waves are briefly discussed. It is shown that the strong correlation among the charged dust grains is a source of dissipation, and is responsible for the formation of the dust-acoustic shock waves. It has been found that the effects of polarization force and non-thermal electrons significantly modify the basic features of such shock waves. It has been proposed to design a new laboratory experiment, which will be able to identify the basic features of the dust-acoustic shock waves predicted in this present investigation.

Dust-acoustic solitary structures in a magnetized dusty plasma with two-temperature nonextensive electrons

The nonlinear propagation of dust-acoustic (DA) waves in an obliquely propagating magnetized dusty plasma, containing nonextensively distributed electrons of distinct temperatures (namely lower and higher temperature nonextensive electrons), negatively charged mobile dust grains, and Maxwellian ions, is rigorously studied and analyzed by deriving the Zakharov-Kuznetsov equation. It is found that the characteristics of the DA solitary waves (DASWs) are significantly modified by the external magnetic field, obliqueness of the system, nonextensivity of the electrons, electron temperature-ratios, and the respective number densities of two species of electrons. The results obtained from this analysis can be employed in understanding and treating the structures and the characteristics of DASWs both in laboratory and astrophysical plasma system.

Non-planar Gardner double layers in two-ion-temperature dusty plasma

Non-planar (cylindrical and spherical) double layers (DLs) in two-ion-temperature dusty plasma, whose constituents are inertial negative dust, ions with two distinctive temperatures, and Boltzmann electrons, are studied by employing the reductive perturbation method. The modified Gardner equation describing the nonlinear propagation of dust-acoustic (DA) waves is derived, and its non-planar double layer solutions are analyzed numerically. The parametric regimes for the existence of DA DLs, which are found to be associated with positive potential only, are obtained. The basic features of non-planar DA DLs, which are found to be different from planar ones, are also identified. The implications of our results to different space and laboratory dusty plasma situations are discussed.

Self-gravitational perturbation in super dense degenerate quantum plasmas

Linear and nonlinear propagation of self-gravitational perturbation mode in a super dense degenerate quantum plasma (containing heavy nuclei/element and degenerate electrons) has been investigated. The linear dispersion relation for this mode (associated with self-gravitational potential) has been derived and analyzed. On the other hand, the nonlinear propagation of this mode in such a degenerate quantum plasma system is examined by the reductive perturbation method, which is valid for a small but finite amplitude limit. It has been found that the nonlinear dynamics of small but finite amplitude self-gravitational perturbation mode in spherical geometry is governed by the modified Korteweg-de Vries (mKdV) equation with negative dispersion coefficient, and the numerical solutions of this mK-dV equation have been analyzed to identify the basic features of spherical self-gravitational potential structures that may form in such a super dense degenerate quantum plasma system. The implications of our results in...