Sagdeev Potential Research Articles

Properties of collisional plasma sheath with ionization source term and two-temperature electrons in an oblique magnetic field

A collisional magnetized plasma sheath with two groups of electrons has been studied using a fluid model including the effects of the ionization source term and the collisional force between ions and neutral atoms. Two kinds of non-Maxwellian descriptions of electron velocity distribution, non-extensive distribution and truncated distribution, are applied in the model, and the ionization effects of both kinds are considered. By applying Sagdeev potential, the modified Bohm sheath criterion is derived. The effects of ionization, magnetic field, and high-temperature electron concentration ratio on plasma sheath density, potential, sheath thickness, and ion kinetic energy are studied. In cases with high background gas density, ion density accumulates at the sheath edge position, forming a peak and manifesting as a rapid drop in the potential profile. The distribution characteristics of electrons have a significant impact on the transport properties of ions. Oscillations and non-monotonic characteristics of net charge near the sheath edge occur as the magnetic field angle increases, leading to an increase in the sheath layer width. It can be seen that in the case of a collisional sheath structure with high-temperature electrons, it is essential to consider the sheath changes induced by the ionization and the collisional force. Compared to a symmetric electron velocity distribution, the actual thickness of the sheath layer in a truncated electron distribution assumption could be significantly reduced.

The characteristics of ion acoustic solitons in nonthermal regularized kappa distributed plasmas

Nonthermal equilibrium is an intrinsic characteristic of space and astrophysical plasmas, and in many space environments, the velocity distributions of charged particles with suprathermal tails may be well be fitted by the Kappa function, which becomes the Maxwellian distribution for κ→∞. Various studies of ion or dusty acoustic solitons, thus, have considered the Kappa distributed electrons in the model calculations. However, the Kappa velocity distribution (KVD) is theoretically not applicable for κ≤3/2. Alternatively, the recently proposed regularized Kappa distribution with two free parameters, κ and α, have been shown to be mathematically and physically smooth for all κ values, which may recover the standard KVD for α=0 and the Maxwellian distribution for κ→∞ and α=0. In this study, we examine the characteristics of ion acoustic solitons based on the linear, weakly nonlinear Korteweg–de Vries (KdV) and fully nonlinear theories with the regularized Kappa distributed electrons and warm ion fluids. These approaches may give rise to the dispersion relation with modified characteristic speed of acoustic waves, the analytical KdV solutions, and the Sagdeev's potential as well as the fully nonlinear solutions. It is shown that the model results are mathematically and physically valid for κ≤3/2 and the formulations with the charges being free parameters are applicable for general acoustic solitons.

Ion acoustic solitary waves in multicomponent plasmas: Influence of ion drift velocity and nonthermal electrons

AbstractIon acoustic solitary waves with arbitrary amplitude have been investigated using the Sagdeev potential (SP) method in a collisionless plasma consisting of non‐isothermal electrons, positrons, and positive ions. The SP has been obtained and the dependence of large amplitude solitary structures on various plasma parameters such as ion drift velocity , non‐thermal parameter , electron to positron temperature ratio , positron density , and Mach number have been studied. It is shown that, for the same values of plasma parameters, accounting for ion drift velocity greatly corrects the solitary wave profile.

The (1+1)-dimensional nonlinear ion acoustic waves in multicomponent plasma containing kappa electrons

Large amplitude (1+1)-dimensional nonlinear ion acoustic waves are theoretically studied in multicomponent plasma consisting of positively charged ions and negatively charged ions, ion beam, kappa-distributed electrons, and dust grains, respectively. By using the Sagdeev potential method, the dynamical system and the Sagdeev potential function are obtained. The important influences of system parameters on the phase diagram of this system are investigated. It is found that the linear waves, the nonlinear waves and the solitary waves are coexistent in the multicomponent plasma system. Meanwhile, the variations of Sagdeev potential with parameter can also be obtained. Finally, it seems that the propagating characteristics of (1+1)-dimensional nonlinear ion acoustic solitary waves and ion acoustic nonlinear shock wave can be influenced by different parameters of this system.

Dust ion acoustic shock and solitary waves in a magnetized multi-component plasma with superthermal electrons

The nonlinear wave propagation in dusty plasmas has received great interest in recent decades due to its significance in interpreting some astrophysical phenomenon. Wave propagation in dust-particle plasmas is likely to differ significantly from that in normal plasmas. Depending on their time scales, several types of acoustic waves propagate in dusty plasmas. The propagation of DIA waves was investigated through a system of multi-component dusty plasma. The study shows the effect of the magnetic field and superthermal parameters on the Sagdeev potential. The Sagdeev potential falls with decreasing ω ci values and rising superthermal parameter k values. Bifurcation analysis is taken into our consideration and shown graphically under the two conditions (A > 0 ) and (A < 0). The presented theoretical work is useful in fully understanding disturbances of the electrostatic in space dusty plasmas.

Theoretical analysis of low frequency dust cyclotron waves with dust charge variations

The propagation of nonlinear dust cyclotron (DC) cnoidal waves having superthermal distributed electrons and ions in the presence of external magnetic field and adiabatic dust charge variation is investigated. The effect of dust charge variation is profoundly modified due to the presence of the superthermal electrons and ions. The dust charge variation parameter decreases with an increase in the superthermality index of ions. Adopting the reductive perturbation approach, it is shown that the dynamics of the cnoidal structure is modeled by a Korteweg–de Vries equation. It is found that only negative potential DC cnoidal and solitary structures are observed in such a plasma. The results further reveal that the cnoidal structures strongly depend on the degree of superthermality, dust charge variation parameter, temperature and number density of fluid particles, angle of obliqueness, as well as on the magnetic field strength. The numerical results confirm that as the dust charge variation enters the picture, amplitude as well as the width of the cnoidal waves enhances. Furthermore, the analysis is performed through Sagdeev potential, plane phase plot and spatial variation of potential to elucidate various aspects of the cnoidal wave dynamics in the presence of the adiabatic dust charge variation.

Effect of trapping in coupled kinetic Alfven-acoustic waves in a partially degenerate plasma with quantizing magnetic field

Inclusion of a quantizing magnetic field in a partially degenerate plasma has interesting effects on the propagation of solitary and nonlinear periodic structures in coupled kinetic Alfven acoustic waves. In this paper, we use two-potential theory to investigate the nonlinear structures using Sagdeev potential approach and further analyze it using nonlinear dynamical methods. It is shown that the existence of solitary structure is sensitive to small temperature effects and quantizing magnetic field in a dense plasma with adiabatically trapped electrons. The work presented here is useful in understanding the low frequency wave propagation in a dense astrophysical environment like white dwarf stars and in low beta laboratory plasmas e.g. intense laser-plasma interactions.

Dust-acoustic periodic travelling waves in a magnetized dusty plasma with trapped ions and nonthermal electrons in astrophysical situations: oblique excitations

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.

Formation of double-layers and super-solitons in a six-component cometary dusty plasma

The formation and main features of the fully nonlinear structure in a six-component dusty plasma system have been investigated using Sagdeev potential approach. By means of pseudo-potential technique, the fluid equations describing the plasma system were diminished into a single nonlinear differential equation, called energy equation modified by presenting the parameters of addition plasma components. For certain values of the configurationally plasma parameters, our findings show that in addition to the solitary waves, double-layers and super-solitons exist and propagate in this plasma system. The main features of these waves have been studied by investigating the associated phase-portrait trajectories and potential curves as well and are found to be very sensitive to the variation of these parameters. The obtained results are mainly relevant to the cometary plasma and it may also provide better and helpful understanding of the nonlinear nature of space, astrophysical and cometary plasmas.Graphical abstractThe formation and main features of the fully nonlinear structure in a six-component dusty plasma system have been investigated using Sagdeev potential approach. By means of pseudo-potential technique, the fluid equations describing the plasma system were diminished into a single nonlinear differential equation, called energy equation modified by presenting the parameters of addition plasma components. For certain values of the configurationally plasma parameters, our findings show that in addition to the solitary waves, double-layers and super-solitons exist and propagate in this plasma system. The main features of these waves have been studied by investigating the associated phase-portrait trajectories and potential curves as well and are found to be very sensitive to the variation of these parameters.

Study on the characteristics of non-Maxwellian magnetized sheath in Hall thruster acceleration region

The secondary electron emission (SEE) and inclined magnetic field are typical features at the channel wall of the Hall thruster acceleration region (AR), and the characteristics of the magnetized sheath have a significant effect on the radial potential distribution, ion radial acceleration and wall erosion. In this work, the magnetohydrodynamics model is used to study the characteristics of the magnetized sheath with SEE in the AR of Hall thruster. The electrons are assumed to obey non-extensive distribution, the ions and secondary electrons are magnetized. Based on the Sagdeev potential, the modified Bohm criterion is derived, and the influences of the non-extensive parameter and magnetic field on the AR sheath structure and parameters are discussed. Results show that, with the decrease of the parameter q, the high-energy electron leads to an increase of the potential drop in the sheath, and the sheath thickness expands accordingly, the kinetic energy rises when ions reach the wall, which can aggravate the wall erosion. Increasing the magnetic field inclination angle in the AR of the Hall thruster, the Lorenz force along the direction acting as a resistance decelerating ions becomes larger which can reduce the wall erosion, while the strength of magnetic field in the AR has little effect on Bohm criterion and wall potential. The propellant type also has a certain effect on the values of wall potential, secondary electron number density and sheath thickness.

Wave breaking limit in arbitrary mass ratio warm plasmas

AbstractThe maximum sustainable amplitude, so‐called wave breaking limit, of a nonlinear plasma wave in arbitrary mass ratio warm plasmas is obtained in the non‐relativistic regime. Using the method of Sagdeev potential, a general wave breaking formula is derived by taking into account the dynamics of both the species having finite temperature. It is found that the maximum amplitude of the plasma wave decreases monotonically with the increase in temperature of the negative species (temperature of the positive species) and increases (decreases) with increase in mass ratio provided , where .

The effects of parameters of Cairns-Tsallis distribution on the properties of ion-acoustic soliton waves in plasma

The specifications of ion-acoustic soliton waves (IASWs) of plasma, including warm fluid ions and Cairns-Tsallis (C-T) distributed electrons and positrons, were investigated. The phase velocity, sagdeev potential, and Korteweg-de Vries (KdV) equation and its solution are obtained using reductive perturbation method (RPM). The results indicated that the parameters α and q have a great effect on phase velocity, nonlinear and dispersive coefficients, Sagdeev potential, maximum amplitude, and width of IASWs.

Nonlinear dynamics in the jupiter magnetosphere: implications of dust-acoustic cnoidal mode

Different types of waves and their nature in the Jovian middle magnetosphere are still not clear or specified. For this purpose, a generalized hydrodynamic model for an arbitrary amplitude dust-acoustic waves is built for true Jovian magnetosphere. The plasma system consists of positive dust grains, Maxwellian ions and electrons. An evolution equation containing a Sagdeev potential is derived, and its numerical analysis is presented. Unexpectedly, the given data yielded cnoidal waves only with positive potential. The effect of the external magnetic field, Mach number, and directional cosine parameters are studied and manipulated. We think that the present results are important in realizing the main waves in the Jovian magnetosphere, and the possible correlation to its particles’ stability and pole acoustic waves.

The existence and propagation of dust acoustic waves in quantum four-component plasma

The existence and propagation of dust acoustic waves in quantum four-component plasma are investigated by employing Sagdeev pseudo-potential. The plasma under consideration consists of both quantum electrons and ions beside negative and positive dust particulates. The general determining equation of the Sagdeev pseudo-potential is obtained, and it is found that the equation is very difficult to integrate. Due to the complexity involved in the structure of Sagdeev potential, this equation can only be solved in some limiting cases, such as semi-classical limit and small amplitude approximation. Our findings support the existence of compressive, rarefactive solitary waves and double layers in our plasma system. The influence of the relevant plasma parameters on the existence and profile of the obtained quantum nonlinear waves has been studied. The implications of the obtained results have wide relevance in the study of space and laboratory quantum dusty plasmas situations such as Jupiter’s magnetosphere, upper and lower mesosphere, and comet tails, as well as in condensed matter systems.

A fully nonlinear solitary wave in six-component dusty cometary plasma

The dynamics of fully nonlinear structure of six-component dusty cometary plasma system with the help of Sagdeev pseudo-potential techniques have been investigated. This plasma system is made up of Oxygen (positively and negatively charged) ion pair, negatively charged dust particles, and kappa distributed ions of Hydrogen, hot solar electrons and slightly colder cometary electrons. The linear analysis is carried out and the linear dispersion relation is obtained and investigated with some relevant plasma parameters. As a result, the velocities in the fluid equations are normalized to a general acoustic speed instead of the particular form of acoustic speed. Employing pseudo-potential approach, the basic equations of plasma system were reduced to a single nonlinear ordinary differential equation (energy-balance). By means of Sagdeev potential curves and bifurcation analysis of phase-portrait, the existence and propagation of nonlinear waves are examined. In addition to the periodic solution, it is shown that the localized negative and positive amplitude electrostatic pulses may (co-) exist and propagate in plasma system depending on the Mach number intervals. The impact of some intrinsic plasma parameters on the main features of the solitary wave electrostatic potential profile and the associated electrostatic field are extensively investigated. The results of this research are relevant to plasmas in both laboratory plasmas and exclusively in space plasmas as, comet tails, rings of giant planets, solar wind, interstellar clouds, etc.

Large-amplitude dust acoustic solitons in an opposite polarity dusty plasma with generalized polarization force

Linear and nonlinear dust acoustic (DA) waves have been investigated in an opposite polarity dusty plasma comprisingnegatively and positively charged dust grains, Maxwellian electrons and ions, including the generalized polarization force effect. The properties of linear DA waves have been significantly altered by the dual dust polarity and polarization force. Large amplitude DA solitons have been discussed in the framework of the Sagdeev potential technique. Our results show that both rarefactive and compressive solitons can exist in such a dusty plasma. The basic features of the Sagdeev potential have been examined under the effect of the polarization force parameter R, the ratio of the charge number of the positive dust to that of the negative dust Z, and the Mach number M. The results show that these parameters play a significant role in determining the region of existence of large amplitude DA solitons.

Nonextensive approach to the effect of electron trapping in the presence of quantizing magnetic field on the propagation of ion acoustic waves

Ion acoustic waves (IAWs) are studied for degenerate trapped electron and non-degenerate ion plasma in the presence of quantizing magnetic field in the Tsallis framework. The presence of a magnetic field induces a trapping effect on degenerated electrons, which is studied using the generalized form of the Fermi–Dirac in the non-extensive framework. An appropriate new electron density is reformulated and reexamined in this statistics. The new expression for electron density is used to study the propagation of ion acoustic waves. The linear dispersion relation for IAWs is derived in the presence of the quantizing magnetic field and a small finite temperature in the framework of q-statistics, there influence on the propagation characteristics of the linear ion acoustic wave is discussed. In arbitrary amplitude, we use the Sagdeev potential showing that rarefactive and compressive ion acoustic solitary wave can exist simultaneously under certain conditions of temperature T, quantizing magnetic field η and the entropic index q. In addition, to study the dynamics of small but finite amplitude ion Acoustics solitary waves. Using the reductive perturbation technique the Korteweg de-Vries equation is established. Our results show that both rarefactive and compressive solitary waves may coexist in a certain range of plasma parameters.

On the formation of spin dependent double layer structure in astrophysical plasmas

AbstractDouble layers (DLs) are nonlinear structures, and are thought to be responsible for particle acceleration in laboratory plasmas and astrophysical plasmas. In this paper, the existence of spin dependent DLs structure is explored using separate spin evolution quantum hydrodynamic model. Based on reductive perturbation method, we derived an extended Korteweg–de Vries (eKdV) equation to demonstrate the existence and nature of DLs. We found that spin polarization significantly enhanced the amplitude of the electrostatic potential associated with DLs. Further, spin polarization also increases the depth and width of the Sagdeev potential. It is noted that the contribution of Bohm potential effect is essential for the formation of DLs structure. Our results may be helpful to explain the phenomenon of particle acceleration in dense astrophysical environments specifically in a white dwarf.

Sheath properties in active magnetized multi-component plasmas

Multi-component active plasmas are modeled in the presence of a constant oblique magnetic field by using the hydrodynamics equations. Assuming the electrons and negative ions have Boltzmann distribution and the positive ions have finite temperature, the sheath formation criterion is derived by analyzing the Sagdeev potential. It is found that the Bohm velocity of positive ions depends sensitively on the plasma parameters such as ion-neutral collision frequency, electron impact ionization frequency, positive and negative ion temperatures, initial densities of the charged particles and direction of the applied magnetic field. Also, using our obtained Bohm criterion, the sheath properties of an active magnetized plasma consisting of electrons and positive and negative ion species are investigated numerically and the results are compared with the results of a similar quiescent plasma.

The effects of suprathermal particles on the existence domain of oblique low-frequency solitary waves in multi-component magnetospheric plasmas

The effect of suprathermal particles is examined on arbitrary amplitude nonlinear low-frequency electrostatic solitary waves propagating obliquely to the ambient magnetic field of the terrestrial magnetosphere using the Sagdeev pseudopotential formalism. The four-component plasma model consists of cold singly charged oxygen ions, hot protons, and two distinct groups of electrons with the latter three having kappa velocity distributions. Our numerical investigations based on comparatively low values for the spectral indices of the two electron species and the hot proton distributions as inferred from time history of events and macroscale interactions during substorms mission data reveal that the coexistence of compressive and rarefactive solitons is suppressed in comparison to the behavior in the presence of Maxwellian species (infinitely large values of kappa). Also, the existence of positive potential solitons is suppressed in an intermediate range of cold oxygen-ion densities. The differences are attributed to the occurrence of singularities in the Sagdeev potential for the chosen set of spectral indices.