R. S. Tiwari

Ion-acoustic dressed solitons in a dusty plasma

Using the reductive perturbation method, equations for ion-acoustic waves governing the evolution of first- and second-order potentials in a dusty plasma including the dynamics of charged dust grains have been derived. The renormalization procedure of Kodama and Taniuti is used to obtain a steady state nonsecular solution of these equations. The variation of velocity and width of the Korteweg-de Vries (KdV) as well as dressed solitons with amplitude have been studied for different concentrations and charge multiplicity of dust grains. The higher-order perturbation corrections to the KdV soliton description significantly affect the characteristics of the solitons in dusty plasma. It is found that in the presence of positively charged dust grains the system supports only compressive solitons. However, the plasma with negatively charged dust grains can support compressive solitons only up to a certain concentration of dust. Above this critical concentration of negative charge, the dusty plasma can support ra...

Ion-acoustic solitons in negative ion plasma with two-electron temperature distributions

Ion–acoustic solitons in a warm positive and negative ion species with different masses, concentrations, and charge states with two electron temperature distributions are studied. Using reductive perturbation method, Korteweg de-Vries (KdV) and modified-KdV (m-KdV) equations are derived for the system. The soliton solution of the KdV and m-KdV equations is discussed in detail. It is found that if the ions have finite temperatures, then there exist two types of modes, namely slow and fast ion-acoustic modes. It is also investigated that the parameter determining the nature of soliton (i.e., whether the system will support compressive or rarefactive solitons) is different for slow and fast modes. For the slow mode, the parameter is the relative temperature of the two ion species; whereas for the fast mode, it is the relative concentration of the two ion species. At a critical concentration of negative ions, both compressive and rarefactive solitons coexist. The amplitude and width of the solitons are discus...

Ion‐acoustic compressive and rarefactive solitons in an electron‐beam plasma system

Using the general formulation of reductive perturbation method, the Korteweg–de Vries (KdV) equation is derived for an electron‐beam plasma with hot isothermal beam and plasma electrons and warm ions. The soliton solution of the KdV equation is discussed in detail. It is found that above a critical velocity of electron‐beam two additional ion‐acoustic soliton branches appear. It is found that corresponding to two linear modes, the system supports the existence of compressive as well as rarefactive solitons depending upon the plasma parameters, while corresponding to other two wave modes, the system supports only rarefactive solitons. The effect of different parameters on the characteristics of solitons have been investigated in detail.

Ion acoustic cnoidal waves and associated nonlinear ion flux in a warm ion plasma

Using periodic boundary conditions in the reductive perturbation method for ion acoustic cnoidal waves in a collisionless, unmagnetized plasma consisting of warm ions and hot isothermal electrons, evolution equations for the first order and second order potential are derived. Determining the nonsecular solution of these coupled equations, expressions for wave phase velocity and averaged nonlinear ion flux are obtained. Variations of wave phase velocity and averaged nonlinear ion flux are examined for different values of wave frequency and ion to electron temperature ratio (Ti∕Te). It is found that wave phase velocity increases with an increase in wave amplitude for a given value of frequency and temperature ratio. But for a given wave amplitude, the wave phase velocity increases as the temperature ratio increases or wave frequency decreases. The averaged nonlinear ion flux associated with the propagation of large amplitude cnoidal waves in plasma is found to be negative, which corresponds to back flow of ...

Propagation of ion-acoustic double layer in an inhomogeneous plasma

Using the reductive perturbation technique, the propagation characteristics of ion-acoustic double layer in a spatially inhomogeneous plasma have been investigated. We have derived a modified Korteweg-de Vries (mKdV) equation with varying coefficients for an inhomogeneous plasma with two Maxwellian electron species. The double layer solution of the mKdV equation is discussed in detail. The present analysis shows that the inhomogeneous plasma density n0 does not affect the amplitude of the double layer, m, whereas its width and velocity are found to decrease as it propagates in the higher density region. It is found that the peak compressed (rarefied) ion density, n1m, corresponding to compressive (rarefactive) double layer increases as the double layer moves along the positive density gradient. The relevance of the present theory to the space plasmas is pointed out.

Obliquely propagating ion-acoustic nonlinear periodic waves in a magnetized plasma with two electron species

Obliquely propagating ion-acoustic nonlinear periodic waves in a magnetized plasma consisting of warm adiabatic ions and two Maxwellian electron species are studied. Using the reductive perturbation method, the Korteweg–de Vries (KdV) equation is derived and its cnoidal wave solution is discussed. It is found that as the amplitude of the cnoidal wave increases, so does its frequency. The effects of variations in the density and temperature ratios of the two electron species, the ion temperature, the angle of obliqueness and the magnetization on the characteristics of the cnoidal wave are discussed in detail. When the coefficient of the nonlinear term of the KdV equation, a 1 , vanishes, the modified Korteweg–de Vries equation is derived, and its periodic-wave solutions are discussed in detail. In the limiting case these periodic-wave solutions reduce to soliton or double-layer solutions.

Ion-acoustic cnoidal wave and associated non-linear ion flux in dusty plasma

Using reductive perturbation method with appropriate boundary conditions, coupled evolution equations for first and second order potentials are derived for ion-acoustic waves in a collisionless, un-magnetized plasma consisting of hot isothermal electrons, cold ions, and massive mobile charged dust grains. The boundary conditions give rise to renormalization term, which enable us to eliminate secular contribution in higher order terms. Determining the non secular solution of these coupled equations, expressions for wave phase velocity and averaged non-linear ion flux associated with ion-acoustic cnoidal wave are obtained. Variation of the wave phase velocity and averaged non-linear ion flux as a function of modulus (k2) dependent wave amplitude are numerically examined for different values of dust concentration, charge on dust grains, and mass ratio of dust grains with plasma ions. It is found that for a given amplitude, the presence of positively (negatively) charged dust grains in plasma decreases (incre...

Effect of nonisothermal electrons on dressed soliton in ion beam plasma system

Using the reductive perturbation method (RPM) evolution equations, governing the first and second order potentials for ion acoustic wave in an ion beam plasma system with nonisothermal electrons, are derived. Adopting renormalization procedure of Kodama and Taniuti [J. Phys. Soc. Jpn. 45, 298 (1978)] nonsecular dressed soliton solution of these coupled equations is determined. An alternative approach is also used to obtain large amplitude soliton solution, retaining higher order nonlinearities in the expansion of the Sagdeev potential and integrating the resulting energy equation for the system. For small amplitude approximation, this solution reduces to dressed soliton solution obtained for the system using the renormalization in the RPM. Variation of the amplitude (A), velocity (λ), width (W), and the product amplitude×width4 (AW4) are numerically studied for the Korteweg–de Vries, dressed and large amplitude soliton for different values of parameters of the beam-plasma system, and results are summarized.

Large amplitude ion-acoustic solitons in dusty plasmas

Characteristics of ion-acoustic soliton in dusty plasma, including the dynamics of heavily charged massive dust grains, are investigated following the Sagdeev Potential formalism. Retaining fourth order nonlinearities of electric potential in the expansion of the Sagdeev Potential in the energy equation for a pseudo particle and integrating the resulting energy equation, large amplitude soliton solution is determined. Variation of amplitude (A), half width (W) at half maxima and the product P = AW2 of the Korteweg-deVries (KdV), dressed and large amplitude soliton as a function of wide range of dust concentration are numerically studied for recently observed parameters of dusty plasmas. We have also presented the region of existence of large amplitude ion-acoustic soliton in the dusty plasma by analyzing the structure of the pseudo potential. It is found that in the presence of positively charged dust grains, system supports only compressive solitons, on the other hand, in the presence of negatively charg...

Large amplitude ion-acoustic double layers in warm dusty plasma

Large amplitude ion-acoustic double layer (IADL) is studied using Sagdeevs pseudo-potential technique in collisionless unmagnetized plasma comprising hot and cold Maxwellian population of electrons, warm adiabatic ions, and dust grains. Variation of both Mach number (M) and amplitude |φ m | of large amplitude IADL with charge, concentration, and mass of heavily charged massive dust grains is investigated for both positive and negative dust in plasma. Our numerical analysis shows that system supports only rarefactive large amplitude IADL for the selected set of plasma parameters. Our investigations for both negative and positive dust grains reveal that ion temperature increases the mobility of ions, resulting in increase in the Mach number of IADL. The larger mobility of ions causes leakage of ions from localized region, resulting into decrease in the amplitude of IADL. Other parameters, e.g. temperature ratio of hot to cold electrons, charge, concentration, mass of heavily charged massive dust grains also play significant role in the properties and existence of double layers. Since it is well established that both positive and negative dust are found in space as well as laboratory plasma, and double layers have a tremendous role to play in astrophysics, we have included both positive and negative dust in our numerical analysis for the study of large amplitude IADL. Further data used for negative dust are close to experimentally observed data. Hence, it is anticipated that our parametric studies for heavily charged (both positive and negative) dust may be useful in understanding laboratory plasma experiments, identifying nonlinear structures in upper part of ionosphere and lower part of magnetosphere structures, and in theoretical research for the study of properties of nonlinear structures.