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A letter to the editor is presented in response to the article "Dust Acoustic Solitary Waves in Dusty Plasma With Nonthermal Ions," by Frank Verheest and colleagues that was published in the February 11, 2010 issue.

In the present paper, the characteristics of the head-on collision between two dust-acoustic solitary waves (DASWs) in an adiabatic dusty plasma consisting of variable negatively charged dust grains, isothermal electrons and two-temperature isothermal ions in the presence of an external oblique magnetic field are investigated. Using the extended Poincaré–Lighthill–Kuo (PLK) method, the Korteweg–de Vries (KdV) equations and the analytical phase shifts after the head-on collision of two solitary waves are derived. The effects of the magnetic field and its obliqueness, two different type of isothermal ions and the dust particles adiabaticity are discussed. It is found that these factors significantly affect the phase shifts. [ABSTRACT FROM AUTHOR]

High rate sampling detectors measuring the potential difference between the main body and boom antennas of interplanetary spacecraft have been shown to be efficient means to measure the voltage pulses induced by nano dust impacts on the spacecraft body itself (see Meyer-Vernet et al. in Sol. Phys. 256:463, ). However, rough estimates of the free charge liberated in post impact expanding plasma cloud indicate that the cloud's own internal electrostatic field is too weak to account for measured pulses as the ones from the TDS instrument on the STEREO spacecraft frequently exceeding 0.1 V/m. In this paper we argue that the detected pulses are not a direct measure of the potential structure of the plasma cloud, but are rather the consequence of a transitional interruption of the photoelectron return current towards the portion of the antenna located within the expanding cloud. [ABSTRACT FROM AUTHOR]

Results from optical photometric observations of the pre-main sequence star GM Cep are reported in the paper. The star is located in the field of the young open cluster Trumpler 37-a region of active star formation. GM Cep shows a large amplitude rapid variability interpreted as a possible outburst from EXor type in previous studies. Our data from BVRI CCD photometric observations of the star are collected from June 2008 to February 2011 in Rozhen observatory (Bulgaria) and Skinakas observatory (Crete, Greece). A sequence of sixteen comparison stars in the field of GM Cep was calibrated in the BVRI bands. Our photometric data for a 2.5 years period show a high amplitude variations ( $\Delta V \sim2\mbox{$.\!\!^{\mathrm{m}}$}3$) and two deep minimums in brightness are observed. The analysis of collected multicolor photometric data shows the typical of UX Ori variables a color reversal during the minimums in brightness. On the other hand, high amplitude rapid variations in brightness typical for the Classical T Tauri stars also present on the light curve of GM Cep. Comparing our results with results published in the literature, we conclude that changes in brightness are caused by superposition of both: (1) magnetically channeled accretion from the circumstellar disk, and (2) occultation from circumstellar clouds of dust or from features of a circumstellar disk. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of the dust acoustic solitary waves in dusty plasmas are studied. The distribution of ions is nonthermal, and the nonthermal parameter is treated as a variable. The pseudo-potential method has been used to investigate the possibility of soliton formation. We show that for some values of the nonthermal parameter there is no soliton. [ABSTRACT FROM AUTHOR]

Obliquely propagating three-dimensional dust-acoustic periodic travelling waves (DAPTWs) in a magnetized dusty plasma composed of negatively charged inertial dust particles, trapped ions, and nonthermal fast electrons have been undertaken. In the dusty plasma model at hand, the dynamic behaviors of DAPTWs are governed by a Schamel equation. The presence of dust acoustic solitary waves (DASWs) and DAPTWs is investigated via bifurcation analysis of the Hamiltonian system. In the nonlinear regime, the Sagdeev potential and phase portrait structures indicate the presence of small-amplitude DAPTW solutions. The influences of intrinsic physical parameters include the strength of the static magnetic field, the obliqueness of propagation, the thermal pressure of charged dust grains, the electron to dust density ratio, the trapping parameter of trapped ions, and the degree of nonthermality of fast electrons on the characteristics of DAPTWs are simulated numerically. In particular, the findings illustrate that the amplitude of DAPTWs is reduced as the numerical values of the trapping parameter are decreased. Interestingly, the theoretical simulations of numerical results can significantly highlight the physical nature of DAPTWs in astrophysical situations such as Earth's magnetosphere, auroral region, and heliospheric environments. [ABSTRACT FROM AUTHOR]

In this paper, regarding the recent detection of significant azimuthal magnetic field in some accretion disks such as protostellar (Donati et al. in Nature 438:466, 2005), the multi-fluid model has been employed to analysis the stability of Keplerian rotational viscous dusty plasma system in a current-free helical magnetic field structure. Using the fluid-Maxwell equations, the general dispersion relation of the excited modes in the system has been obtained by applying the local approximation method in the linear perturbation theory. The typical numerical analysis of the obtained dispersion relation in the high-frequency regime shows that the presence of azimuthal magnetic field component in Keplerian flow has a considerable role in the stability conditions of the system. It also shows that the magnetic field helicity has a stabilization role against the magnetorotational instability (MRI) in the system due to contraction of the unstable wavelength region and decreasing the maximum growth rate of the instability. In this sense, the stabilization role of the viscosity term is more considerable for HMRI (instability in the presence of azimuthal magnetic field component) than the corresponding MRI (instability in the absence of azimuthal magnetic field component). Moreover, considering the discovered azimuthal magnetic field in these systems, the MRI can be arisen in the over-all range of dust grains construction values in contract with traditional MRI. This investigation can greatly contribute to better understanding the physics of some astrophysical phenomena, such as the main source of turbulence and angular momentum transport in protostellar and the other sufficiently ionized astrophysical disks, where the azimuthal magnetic field component in these systems can play a significant role. [ABSTRACT FROM AUTHOR]

The magnetorotational instability (MRI) in axisymmetric rotating dusty plasmas with viscous effects is investigated by means of a three-component model MRI with a vertical weak magnetic field. Starting from the three-fluid equations and Maxwell's equations, I derive the general linear dispersion relation governing local MRI. The dust rotational flow is assumed to have the same angular velocity as ions and electrons. The dispersion relation of two special cases, without viscosity and dust effects respectively, is discussed in detail by taking into account the high-frequency approximation in order to make the perturbation frequency larger than the ion cyclotron frequency. The numerical results demonstrate that both the viscosity and dust effects can prevent the MRI growth, and the dust-induced effects are shown to be especially significant. [ABSTRACT FROM AUTHOR]

The KdV equation is derived for weakly nonlinear ion-acoustic waves in an unmagnetized warm dusty plasma with electron inertia. It has been shown that the inclusion of electron inertia and pressure variation of the species not only significantly modifies the basic features (width and amplitude) of dust ion-acoustic solitions, but also introduces a new parametric regime for the existence of positive and negative solitons. [ABSTRACT FROM AUTHOR]

The linear and weakly nonlinear dust-ion-acoustic wave propagation obliquely to an external magnetic field is studied in a magnetized dusty plasma which consists of magnetized fluid ions bearing with anisotropic pressure, suprathermal electrons, and static dust grains. In the linear regime, the magnetized dusty plasma supports the propagation of the fast electrostatic dust-ion-cyclotron (EDIC) and the slow electrostatic dust-ion-acoustic (DIA) modes. The effects of different parameters on the two modes are outlined. In the weakly nonlinear regime, a reductive perturbative technique (RPT) is used to derive a modified equation of propagation of the electrostatic potential modified by the presence of a magnetic field and the ion pressure anisotropy. Particular equations of propagations are covered in the case of unmagnetized anisotropic plasma and the case of a strong magnetic field. It is found numerically that the modified equation of propagation admits compressive and rarefactive solitary waves with amplitudes and widths values increase with the increase of the values of the ion perpendicular pressure. The strength of the magnetic field only affects the width of the two structures. For particular values of plasma parameters, periodic, quasi-periodic, and chaotic nonlinear oscillations are numerically investigated. This chaotic behavior is corroborated by the positivity of one of the Lyapunov exponents. [ABSTRACT FROM AUTHOR]

Starting from one dimensional Kappa distribution for electrons, we have systematically developed the combined Kappa-Cairns distribution. We have found the effective bounds of both nonthermal parameters κ and β e for the combined Kappa-Cairns distribution. This distribution can generate more highly energetic particles in comparison with both Kappa and Cairns distributions. We have investigated ion acoustic solitary structures in a collisionless magnetized plasma composed of negatively charged static dust grains, adiabatic warm ions and a population of highly energetic electrons generated from the combined Kappa-Cairns distribution. Sagdeev pseudo-potential technique has been considered to investigate the arbitrary amplitude steady state solitary structures including double layers and supersolitons. We have developed a computational scheme to draw the existence domains showing the nature of existence of different solitary structures. Different solitary structures of both positive and negative polarities have been observed for different values of κ and β e . We have seen two important transitions of solitary structures for negative polarity, viz., soliton before the formation of double layer → double layer → supersoliton → soliton after the formation of double layer, and soliton before the formation of supersoliton → supersoliton → soliton. For the second case, we have a supersoliton structure without the formation of double layer and this case is completely new one for magnetized plasma. Different solitary structures supported by the system have been investigated with the help of compositional parameter spaces and the phase portraits of the dynamical systems describing different solitary structures. [ABSTRACT FROM AUTHOR]

A theoretical study has been presented to examine the properties of the nonlinear dust-ion-acoustic (DIA) rogue waves in a dusty plasma composed of positive warm ions fluid, immobile negative dust, and non-Maxwellian electrons. By utilizing reductive perturbation method, the Gardner/Extended Korteweg-de Vries equation is deduced. The Extended Korteweg-de Vries (EKdV) equation was converted to nonlinear Schrödinger equation (NLSE) by using a suitable transformation to study the regions of DIA rogue wave propagation. The alteration of the properties of the rogue waves with pertinent plasma parameters is investigated, such as the temperature ratio of the ions-to-electrons, the negative charge located on the dust grains and nonthermality/superthermality/nonextensivity of electrons. And add to that, the first- and second-order dust-ion-acoustic rogue waves nonlinear structures in the system are examined. It is confirmed that the real enforcement of our results is in laboratory experiments and in space plasma (e.g., Earth's magnetosphere, auroral region, heliospheric environments, solar atmosphere, etc.). [ABSTRACT FROM AUTHOR]

An investigation of dust acoustic shock waves in dusty plasma containing two temperature ions is presented. The present investigation is motivated by the observations of Geotail spacecraft that report the occurrence of two temperature ion populations in Earth's magnetotail. We have derived Burgers equation to study dust acoustic shock structures in an unmagnetized plasma with two temperature superthermal ions. We have also derived the modified Burgers equation at critical values of physical parameters for which nonlinear coefficient ( $A$ ) of Burgers equation vanishes. The numerical analysis is performed in context with observations in Earth's magnetotail and the influence of various plasma parameters viz. ions temperature ratio, superthermality of hot and cold ions, kinematic viscosity etc. has been observed on characteristics of DA shocks. It is observed that the amplitude of positive shocks via Burgers equation decreases whereas that of modified shocks with higher order nonlinearity increases with increase in superthermality of cold ions. [ABSTRACT FROM AUTHOR]

The nonlinear features of dust ion-acoustic shock waves (DIASWs) in a magnetoplasma containing cold positive ions, nonextensive electrons, and immobile negatively charged dust grains taking into account the cold ion kinematic viscosity are investigated. The reductive perturbation technique is used to derive a Zakharov-Kuznetsov-Burgers (ZK-Burgers). It is found that the fundamental properties of the DIASWs are significantly modified by the different system parameters such as the nonextensive parameter, the ion gyrofrequency, the dust concentration, the viscosity parameter, and the direction cosines. Also, the polarities (positive and negative shocks) of the potential are found to exist in the plasma under consideration. The implications of our results may be used in understanding the acoustic shock waves propagation in laboratory and space plasmas. [ABSTRACT FROM AUTHOR]

The properties of linear dust acoustic (DA) waves in inhomogeneous viscous dusty plasmas with non-thermal electrons and ions have been investigated. A linear dispersion relation is obtained with the non-adiabatic dust charge fluctuation and fraction of nonthermality of electron-ion. The dependence of frequency and the damping rate of waves on the nonthermality fraction and dust kinematic viscosity coefficient are discussed. To study the dust acoustic shock waves, KdV-Burgers (KdV-B) equation for homogeneous dissipative dusty plasma has been considered and solved by means of tanh method. The obtained solution is a particular combination of a solitary wave with a Burgers shock wave. The present results are useful in the context of space plasma. [ABSTRACT FROM AUTHOR]

The nonlinear amplitude modulation of dust-ion acoustic wave (DIAW) is studied in the presence of nonextensive distributed electrons in dusty plasmas with stationary dust particles. Using the reductive perturbation method (RPM), the nonlinear Schrödinger equation (NLSE) which governs the modulational instability (MI) of the DIAWs is obtained. Modulational instability regions and the growth rate of nonlinear waves are discussed. It is shown that the wave characters are affected by the value of nonextensive parameter and also relative density of plasma constituents. [ABSTRACT FROM AUTHOR]

Properties of dust-ion acoustic solitary waves (DIASWs) in dusty plasmas composed of nonextensive electrons, cold fluid ions and stationary dust particles are investigated. The possibility of soliton formation and the effect of nonextensivity of the electron distribution on the soliton characters are studied using the pseudo-potential method. Regions of parameters in which a solitary wave can be propagated in the plasma is analyzed too. It is found that the solitary excitations strongly depend on the electron-ion density ratio ( μ), Mach numbers ( M) as well as the nonextensive parameter ( q). It is shown that the domain of allowed Mach numbers depends drastically on the plasma parameters and especially on the electron nonextensivity. It is found that beyond a threshold value of the nonextensive parameter ( q), dust-ion acoustic solitons are admitted. [ABSTRACT FROM AUTHOR]

On 2012 July 11, two solar filaments were observed in the northeast of the solar disk and their eruptions due to the interaction between them are studied by using the data from the Solar Dynamics Observatory (SDO), Solar TErrestrial RElations Observatory (STEREO) and Global Oscillation Network Group (GONG). The eastern filament (F1) first erupted toward the northeast. During the eruption of F1, some plasma from F1 fell down and was injected to the North-East part of another filament (F2), and some plasma of F1 fell down to the northern region close to F2 and caused the plasma to brighten. Meanwhile, the North-East part of F2 first started to be active and rise, but did not erupt finally. Then the South-West part of F2 erupted successfully. Therefore, the F2's eruption is a partial filament eruption. Two associated CMEs related to the eruptions were observed by STEREO/COR1. We find two possible reasons that lead to the instability and the eruption of F2. One main reason is that the magnetic loops overlying the two filaments were partially opened by the eruptive F1 and resulted in the instability of F2. The other is that the downflows from F1 might break the stability of F2. [ABSTRACT FROM AUTHOR]

Nonlinear propagation of dust-acoustic (DA) waves in a magnetized dusty plasma, consisting of negatively charged mobile dust, Maxwellian ions and two distinct temperature nonextensive electrons (following nonextensive q-distribution each), has been studied and analyzed by deriving and solving the Korteweg-de-Vries (K-dV) equation. According to the outcomes of the investigation, the basic characteristics of the DA solitary profiles are found to be strongly modified by the external magnetic field, nonextensivity of the electrons and the respective number densities of the two species of electrons. The results of this investigation can be applied in both laboratory and astrophysical plasma scenarios for understanding the basic features of the localized electrostatic dust-acoustic solitary waves (DASWs). [ABSTRACT FROM AUTHOR]

In the new investigation of dust-ion acoustic (DIA) waves with negative dust charges and weakly relativistic ions and electrons in the plasma, compressive and rarefactive DIA solitons of interesting characters are established through the Korteweg-de Vries (KdV) equation. Eventually, the amplitudes of the compressive DIA solitons are found to be constant at some critical temperature ratio α (electron to ion temperature ratio) identifying some critical dust charge Z. It is predicted, that the reception of dust charges by the plasma particles at the variation of temperature starts functioning to the growth of compressive soliton's constant stage of amplitude after the state of critical α. The identification of critical dust charge ( Z) which is found to be very great for solitons of constant amplitudes becomes feasible for very small dust to ion density ratio ( σ). But it can be achieved, we observe, due to the relativistic increase in ion-density as in mass, which is also a salient feature of this investigation. [ABSTRACT FROM AUTHOR]

The head-on collisions of dust-acoustic waves (DAWs) in a dense magnetized quantum dusty plasma are investigated by using the extended version of the Poincaré-Lighthill-Kuo (PLK) method. We discuss the theoretical predictions as regards the existence of compressive and rarefactive DAWs in the model. We also observe that, in the generic case, collisions are possible among the same polarity solitons, whereas in the special case, collisions are possible among the same or opposite polarity solitons. It is also observed that the phase shifts are significantly affected by the quantum diffraction parameter and the dust cyclotron frequency. The interesting observations of this manuscript are that the waves reach a maximum amplitude which is a superposition of the initial amplitude and they suffer a time delay during their collision. Our results may be useful in space and laboratory plasmas as well as in plasma applications. [ABSTRACT FROM AUTHOR]

Alternative localized dust-ion acoustic waves are investigated in a magnetized charge varying dusty plasma with nonthermal electrons having a vortex-like velocity distribution. The correct non-Maxwellian charging currents are obtained based on the well-known orbit limited motion theory. Following the standard reductive perturbation technique, a Schamel-Zakharov Kuznetsov Burgers (S-ZKB) equation is derived. It is shown that due to an interplay between trapping and nonthermality, our dusty plasma model may support solitary as well as shock waves the main quantities (phase velocity, amplitude and width) of which are drastically influenced by trapping, nonthermality and charge variation. Due to the flexibility provided by the outlined distribution function (two concepts of non isothermality), we stress that our model should provide a good fit of the space observations. [ABSTRACT FROM AUTHOR]

Nonlinear propagation of dust-acoustic waves in an unmagnetized dusty plasma consisting of negatively charged mobile dust, nonextensive ions following nonextensive q-distribution and two distinct temperature superthermal electrons following superthermal kappa distribution each, is investigated by employing lower and higher order nonlinear equations, namely the Korteweg-de-Vries (K-dV), the modified Korteweg-de-Vries (mK-dV) and the Gardner equations. The characteristic features of the hump (positive potential) and dip (negative potential) shaped dust-acoustic (DA) Gardner solitons are found to exist beyond the K-dV limit. The effects of two superthermal temperature electrons and ions nonextensivity on the basic characteristics of DA K-dV, mK-dV and Gardner solitons have also been investigated. It has been found that the DA Gardner solitons exhibit either negative or positive potential solitons only for q< q where, q is the critical value of the nonextensive parameter q. The possible applications of our results in understanding the localized nonlinear electrostatic structures existing in solar atmosphere, Saturn's magnetosphere etc. (where the tails of the high energetic particles at different temperatures follow power-law like distribution) are also briefly discussed. [ABSTRACT FROM AUTHOR]

The propagation of dust ion acoustic waves is studied in plasmas composed of superthermal distributed electrons and stationary dust particles. The nonlinear Schrödinger equation is derived using the reductive perturbation technique and the modulational instability of dust ion acoustic waves is analyzed. Parametric investigations indicate that the presence of superthermal distributed electrons significantly modify the modulational instability and its growth rate. The effect of particle relative density on the wave characters is also investigated. [ABSTRACT FROM AUTHOR]

The dust-acoustic shock waves have been theoretically investigated using reductive perturbation technique. An unmagnetized four-component dusty plasma system consisting of nonextensive q-distributed electrons, Boltzmann distributed ions, and negatively as well as positively charged dust particles has been considered. The solution of Burgers equation in planar geometry is numerically analyzed. It has been observed that the nonextensive q-distribution of electrons has a significant role in the formation of shock waves. The relevance of our results to astrophysics as well as laboratory plasmas are briefly discussed. [ABSTRACT FROM AUTHOR]

This theoretical investigation has been made on dust-acoustic (DA) waves containing nonextensivity of electrons being two different temperatures, negatively charged dust grains, and Maxwellian ions. The Zakharov-Kuznetsov (Z-K) equation has been derived and numerically solved to analysis the basis features. It is observed that the characteristics of the DA solitary waves (DASWs) are significantly modified by the external magnetic field with the different temperatures for electrons followed by the nonextensive distribution. The results obtained from this analysis can be employed in understanding the nature of plasma waves both in laboratory and space plasma system. [ABSTRACT FROM AUTHOR]

A rigorous theoretical investigation has been made on the obliquely propagating dust-acoustic (DA) waves in a magnetized dusty plasmas consisting of distinct temperature q-distributed electrons with distinct strength of nonextensivities, nonthermal ions and negatively charged mobile dust grains, and analyzed by deriving the Zakharov-Kuznetsov equation. It is found that the characteristics and the properties of the DA solitary waves (DASWs) are significantly modified by the external magnetic field, relative temperature ratio of ions, relative number densities of electrons as well as ions, the nonextensivity of electrons, nonthermality of ions and the obliqueness of the system. The possible implications of the results obtained from this analysis in space and laboratory dusty plasmas are briefly addressed. [ABSTRACT FROM AUTHOR]

The characteristics of longitudinal dust acoustic wave (DAW) in presence of velocity shear have been investigated in a strongly coupled dusty plasma using the generalized hydrodynamic (GH) model. In the hydrodynamic regime ( ωτ≪1), i.e. when characteristic time τ is slower than inverse of wave frequency, the viscosity in the GH model plays the usual role of wave damping, whereas in the kinetic regime ( ωτ≫1), i.e. when characteristic time τ is larger than inverse of wave frequency, viscosity shows energy storing property in the wave. In the kinetic regime, we have studied the longitudinal mode $\omega^{2}=k^{2} (c_{d}^{2}+c_{l}^{2})$ (where ω is the frequency, k is the wave number, c is the dust acoustic velocity and c is the longitudinal velocity that arises due to viscosity) in presence of velocity shear. It is shown that velocity shear can destabilize this mode. Both nonmodal and modal techniques are employed to demonstrate the growth rate of the instability. [ABSTRACT FROM AUTHOR]

The coupling of Shukla-Varma (SV) and convective cell modes is discussed in the presence of non-Boltzmannian electron response and parallel equilibrium shear flow. In the linear case, a new dispersion relation is derived and analyzed. It is found that the coupled SV and convective cell modes destabilize in the presence of electron shear flow. On the other hand, in the nonlinear regime, it is shown that Shukla-Varma mode driven counter rotating vortices can be formed for the system under consideration. It is found that these vortices move slowly by comparison with the ion acoustic or electron drift-wave driven counter rotating vortices. The relevance of the present investigation with regard to space plasmas is also pointed out. [ABSTRACT FROM AUTHOR]

It is shown that the sheared flow of electrons and ions in the presence of heavy stationary dust gives rise to unstable Alfvén waves. The coupling of newly studied low frequency electrostatic current-driven mode with the electromagnetic Alfvén and drift waves is investigated. The instability conditions and the growth rates of both inertial and kinetic Alfvén waves are estimated. The theoretical model is applied to the night side boundary regions of Jupiter’s magnetosphere which contain positive dust. The growth rates increase with increase in sheared flow speed. In the nonlinear regime, both inertial and kinetic Alfvén waves form dipolar vortices whose speed and amplitude depend upon the magnitude of the zero-order current. [ABSTRACT FROM AUTHOR]

Linear and nonlinear analysis are presented for an electronegative dusty plasma system. Linear analysis shows that the dispersive nature of the plasma system changes considerably due to the presence of nonthermal q-nonextensive distributed electrons. The presence of both compressive and rarefactive Sagdeev solitons is investigated and shown that the addition of even a small population of dust particles will significantly modify the large amplitude Sagdeev solitons. The coexistence of both compressive and rarefactive solitons for a certain set of parameters is also noticed in such system. The effect of variation of entropic index q, θi (ratio of positive ion temperature to electron temperature), θn (ratio of negative ion temperature to electron temperature) and dust particles concentration ( R) is elaborated with the help of suitable parameters. [ABSTRACT FROM AUTHOR]

The time fractional modified KdV, the so-called TFMKdV equation is solved to study the nonlinear propagation of the dust acoustic (DA) solitary waves in un-magnetized four components dusty plasma. This plasma consists of positively charged warm adiabatic dust, negatively charged cold dust, non-isothermal electrons and Maxwellian ions. The TFMKdV equation is derived by using semi-inverse and Agrawal’s method and solved by the Laplace Adomian decomposition method (LADM). The effects of the time fractional order ( β), the ratio of dust to ion temperature ( δd), the time ( τ), the mass and charge ratio ( α), the non-isothermal parameter ( γ) and wave velocity ( v) on the DA solitary wave are studied. Our results show that the variations of the amplitude of DA solitary wave versus ( γ) are in agreement with the results obtained previously. Moreover, the time fractional order plays a role of higher order perturbation in modulating the soliton shape. The achievements of this research for the DA solitary waves may be applicable in space plasma environments and laboratory plasmas. [ABSTRACT FROM AUTHOR]

Small amplitude dust-acoustic solitary waves in an unmagnetized dusty plasma consisting of electrons and two temperature ions obeying the q-nonextensive distribution are investigated. Employing reductive perturbation method, the Korteweg-de Vries (KdV) equation is derived. From the solitonic solutions of KdV equation, the influence of nonextensivity of electrons as well as ions and dust concentration on the amplitude and width of dust-acoustic solitary waves has been studied. It is observed that both positive and negative potential dust acoustic solitary waves occur in this case. The modified KdV (mKdV) equation is derived in order to examine the solitonic solutions for the critical plasma parameters for which KdV theory fails. The parametric regimes for the existence of mKdV solitons and double layers (DLs) have also been determined. Positive potential double layers are found to occur in the present study. [ABSTRACT FROM AUTHOR]

A rigorous theoretical investigation on the characteristics of dust-ion-acoustic (DIA) shock waves in an unmagnetized multi component electron-positron-ion dusty plasma (consisting of inertial ions, electrons of two distinct temperatures referred to as low and high temperature superthermal electrons where superthermality is introduced via the κ-type of nonthermal distribution, Boltzmann distributed positrons, and negatively charged immobile dust grains) has been made both theoretically and analytically. The hydrodynamic equation for inertial ions has been used to derive the Burgers equation. The influence of superthermal electrons, Maxwellian positrons and ion kinematic viscosity, which are found in this investigation, significantly modify the basic features of DIA shock waves, are briefly discussed. The present investigation can be very effective for studying and understanding the basic characteristics of shock wave propagation through different astrophysical situations where distinct temperature superthermal electrons dominate the wave dynamics. [ABSTRACT FROM AUTHOR]

The reductive perturbation method has been used to derive the Burgers equation for dust acoustic shock waves in unmagnetized plasma having electrons, singly charged ions, hot and cold dust species with Boltzmann distributions for electrons and ions in the presence of the cold (hot) dust viscosity coefficients. The time-fractional Burgers equation is formulated using Euler-Lagrange variational technique and is solved using the variational-iteration method. The effect of time fractional parameter on the behavior of the shock waves in the dusty plasma has been investigated. [ABSTRACT FROM AUTHOR]

A rigorous theoretical investigation has been made on the nonlinear structures, mainly, dust-acoustic (DA) solitary and shock waves propagating in a strongly coupled dusty plasma consisting of strongly coupled correlated positively and negatively charged inertial cold dust fluid, weakly correlated inertialess Maxwellian electron and ion fluids. The presence of arbitrary (negative and positive) charged dust grains in such a plasma system causes the presence opposite potentials (positive and negative) DA solitary and shock structures and significantly modify it's basic features. The results obtained from this analysis can be employed in understanding the nature of plasma waves both in laboratory and space plasma system. [ABSTRACT FROM AUTHOR]

The problems of large amplitude double layers are discussed using Sagdeev's pseudo-potential technique for a dusty plasma comprising two temperature isothermal ions and nonextensive nonthermal velocity distributed electron. For different sets of plasma parameter values, the Sagdeev potential V( ϕ) has been plotted. It is found that nonextensive q parameter plays a significant role in determining the shape and size of large amplitude double layers. Also, it is observed that the existence of large amplitude double layers depends on different plasma parameters. [ABSTRACT FROM AUTHOR]

The instability of dust ion acoustic waves (DIAWs) driven by ions and electrons with different drift velocities in an unmagnetized, collisionless, isotropic dusty plasma was investigated. The electrons, ions and dust particles are assumed to be the generalized q-nonextensive distributions. The spectral indices of the q-distributions for the three plasma components are different from each other. Based on kinetic theory, the dispersion relation and the instability growth rate of DIAWs are obtained. It is found that the presence of the nonextensive distribution electrons and ions significantly modify the domain of the instability growth rate, as well as the ion-electron density ratio ( ρ) and drifting-thermal velocity ratio ( u/ v). In reverse, the index of dust grains has nearly no any effect on the instability growth rate. Furthermore, the effects of these parameters on the growth rate have also been discussed in detail. [ABSTRACT FROM AUTHOR]

Linear and nonlinear propagation of dust drift waves are investigated in the presence of Cairns and Kappa distributed ion population and Boltzmannian electrons. It is found the frequency of the dust drift wave is greatest for the Cairns, intermediate for Kappa and the least for the Maxwellian distributed ions. Using the drift approximation, a nonlinear equation is derived for the dust drift shock waves which reduces to a Korteweg-de Vries-Burgers (KdVB)-like equation in the comoving frame of reference. The solution of the KdVB-like equation is obtained using the tanh method. It is found that the non-Maxwellian ion population, dust neutral collision frequency as well as the inverse dust density scale length inhomogeneity alter the propagation characteristics of the nonlinear dust drift shock waves. Interestingly, it is found that the non-Maxwellian ion population modifies the scale lengths over which the nonlinear structures are formed. The work presented here may be useful to understand the low frequency electrostatic shock waves in inhomogeneous dusty plasmas such as those found in planetary environments. [ABSTRACT FROM AUTHOR]

Nonplanar (cylindrical and spherical) double layers (DLs) in a quantum dusty plasma (composed of inertial ions, Fermi electrons, and negatively charged immobile dust particles) are studied by employing the reductive perturbation method. The modified Gardner equation describing the nonlinear propagation of the quantum dust ion-acoustic (QDIA) waves is derived, and its nonplanar double layer solutions are numerically analyzed. The parametric regimes for the existence of the DLs, which are found to be associated with both positive and negative potential, are obtained. It has been found that the existence of small but finite amplitude electrostatic double layers depends on β= Z n/ Z n (where Z ( Z) is the charge states for positive ions (negative ions) and n ( n) is the equilibrium positive ions (negative ions) number density) as well as the quantum diffraction parameter, H. It has been also found that the propagation characteristics of nonplanar QDIA DLs are significantly differ from those of planar ones. [ABSTRACT FROM AUTHOR]

Dust-acoustic (DA) solitary waves are investigated in a magnetized dusty plasma comprising cold dust fluid and kappa-distributed ions and/or electrons. The influence of suprathermal particles, obliqueness, and ion temperature on the DA solitary waves is investigated. We find that only negative DA solitary waves will be excited in this model. Also it is shown that the amplitude of the DA solitary wave decreases with deviation of electrons or ions from Maxwellian distribution via decrease of κ or κ. The effect of the temperature of the ion decreases with the amplitude and steepness of the solitary wave front. [ABSTRACT FROM AUTHOR]

The longitudinal fast solitary waves induced by weakly relativistic positron showers of astrophysical origin are studied in a plasma system contaminated with some massive impurities in presence of superthermal effects. The superthermal effects are due to the high energy electrons. The impurities are dust corpuscles with positive and negative charges. It is noticed that increase in the kappa parameter of electrons and relativistic streaming factor of weakly relativistic positron shower, negative dust concentration invoke an enhancement in the strength of solitary wave. On the other hand increase in the shower's temperature as well as positive dust concentration diminish the solitary hump strength. It is worth to mention that only hump type compressive fast solitary waves are predicted by our model, for the given set of plasma parameters, because the convective coefficient of the nonlinear governing equation for solitary wave remains positive in considered regime of interaction for plasma and positron shower. Our calculations in linear regime predict both the fast and slow positron shower induced longitudinal, electrostatic perturbations. Our results may be of importance in understanding the nonlinear propagation of waves in doped astrophysical superthermal plasmas with relativistic positron showers. [ABSTRACT FROM AUTHOR]

Making use of the Sagdeev pseudo-potential approach, we derive the energy like equation for dust-acoustic (DA) solitary waves in a complex plasma having negatively charged cold dust, and electrons/ions featuring the Tsallis distribution. The effects of electron and ion nonextensivity on the DA soliton profile are examined. It is shown that depending on the strength of particle nonextensivity, our plasma model may admit compressive as well as rarefactive DA solitary waves. Our results complement previously published results on this problem. [ABSTRACT FROM AUTHOR]

The properties of small but finite amplitude dust acoustic (DA) shock waves are studied in a charge varying dusty plasma with ions and electrons having kappa velocity distribution. We obtain the global Debye length including the influence of suprathermality effects and dust charge fluctuations. It is shown that the effects of suprathermality of ions/electrons and dust charge fluctuation significantly modify the basic properties of DA shock wave. We observe that only negative DA shock waves will be excited in this model. The amplitude of DA shock wave increases with deviation of electrons or ions from Maxwellian distribution via decrease of spectral index, κ ( j= i, e denotes, ions and electrons, respectively). Also, it is indicated that the amplitude and steepness of the shock front decreases with an increase in the ion temperature. [ABSTRACT FROM AUTHOR]

A response from Hamid Reza Pakzad to a letter to the editor on the article "Dust Acoustic Solitary Waves in Dusty Plasma With Nonthermal Ions," by Frank Verheest and colleagues that was published in the February 11, 2010 issue is presented.

Dust acoustic double layers are studied in a four component dusty plasma comprising positively and negatively charged dust grains, Boltzmann distributed ions and kappa distributed electrons. The conditions for existence of double layers are studied in detail using Sagdeev's method. Large amplitude double layers are obtained for a range of values of the plasma parameters. [ABSTRACT FROM AUTHOR]

Progress in understanding the nonlinear features of dust-acoustic waves (DAWs) which accompany a collisional strongly and weakly coupled unmagnetized dusty plasma with Boltzmann distributed electrons, ions and negatively charged dust grains is presented. By using a hydrodynamic model, the Korteweg-de Vries-Burgers (KdV-Burgers) equation is derived. The existence regions of the solitary pulses are defined precisely. Furthermore, numerical calculations reveal that, due to collisions, the DAWs damp waves and the damping rate of the waves depends mainly on the collision frequency. The collisions are found to significantly change the basic properties of the DAWs. The effects of electron-to-ion concentration ratio, and ion-to-electron temperature ratio have important roles in the behavior of the DAWs. The results may have relevance in space and laboratory dusty plasmas. [ABSTRACT FROM AUTHOR]

Nonlinear dust acoustic (DA) localized structures are studied in two-suprathermal ion-temperature dusty plasma. The electron number density is assumed to be sufficiently depleted owing to the electron attachment during the dust charging process, i.e. n≪ n. The DA solitary waves and double-layers are investigated based on the pseudo-potential approach. It is found that the ion suprathermality may affect the spatial patterns as well as the nature of the DA structures. [ABSTRACT FROM AUTHOR]

In this work, we consider the formation of electrostatic, dust-acoustic solitary structure in a unmagnetized plasma with Lorentzian electrons (kappa-distributed) and more than one species of thermal ions (Maxwellian). The work is inspired by results of different space-based observations of electrostatic solitary waves (ESW) in the near-earth and magnetospheric plasmas and recent experimental realization of existence of superthermal electron component in various space plasmas. We have, in this work, shown that existence of compressive potential structure is possible only with more than one species of thermal ions. Besides, formation of compressive double layers is also possible which depends on the amount of deviation of the electron thermal velocities from a Maxwellian distribution. We show that both dust-temperature and super-thermal electrons lead to a decrease in the soliton amplitude. [ABSTRACT FROM AUTHOR]