Arshad M. Mirza

Ion acoustic shock waves in electron-positron-ion quantum plasma

Ion acoustic shock waves (IASWs) are studied in an unmagnetized quantum plasma consisting of electrons, positrons, and ions employing the quantum hydrodynamic (QHD) model. Nonlinear quantum IASWs are investigated by deriving the Korteweg–deVries–Burger equation under the small amplitude perturbation expansion method. The dissipation is introduced by taking into account the kinematic viscosity among the plasma constituents. It is found that the strength of the ion acoustic shock wave is maximum for spherical, intermediate for cylindrical, and minimum for planar geometry. The temporal evolution of the shock for a quantum e-p-i plasma in a spherical geometry is also investigated. It is found that the strength and the steepness of the quantum ion acoustic shock wave increases with decreasing stretched time coordinate (representing slow time scale) ∣τ∣. It is also found that an increase in the quantum Bohm potential decreases the strength as well as the steepness of the shock. The temporal evolution of the qua...

Modulation instability of low-frequency electrostatic ion waves in magnetized electron-positron-ion plasma

The nonlinear amplitude modulation of low-frequency electrostatic ion waves propagating in collisionless magnetized electron-positron-ion plasma are studied. The Krylov–Bogoliubov–Mitropolsky perturbation method is employed to derive the nonlinear Schrodinger equation. Modulation instability of both ion-acoustic and ion-cyclotronlike modes is examined. We found that the ion-acoustic mode, which propagates below the ion-cyclotron frequency, is stable if the strength of the external magnetic field is small. However, as the strength of the magnetic field increases, this mode becomes modulationally unstable for a range of wave numbers and angles of propagation. This range increases as the strength of the magnetic field and/or positron density increases. For the ion-cyclotronlike mode, which propagates above the ion-cyclotron frequency, a number of stability/instability regions appear in the (kc,θ) plane even for a very small value of the magnetic field. It is found that, for both modes, critical wave number k...

CYLINDRICAL AND SPHERICAL ION-ACOUSTIC SOLITONS IN ADIABATICALLY HOT ELECTRON–POSITRON–ION PLASMAS

Cylindrical and spherical ion-acoustic solitons in electron–positron–ion plasma have been investigated. The reductive perturbation method has been used to derive a modified Korteweg-de-Vries (mKdV) equation. The numerical solutions of the mKdV equation are presented for both geometries. We found that the amplitude and width of ion-acoustic solitons decrease with an increase in positron concentration. It is also shown that adiabatically hot ions play a destructive role in the formation of solitons in both geometries.

Nonlinear electrostatic waves in a magnetized dust-ion plasma

It is shown that the nonlinear equation governing the dynamics of coupled dust-acoustic and dust-cyclotron waves in a magnetized dust-ion plasma can be written in the form of an energy integral. The latter is analyzed analytically as well as numerically to investigate the properties of arbitrary amplitude solitary waves. It is found both analytically as well as numerically that there exist solitary waves only with a negative potential. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring systems and cometary tails, are briefly discussed.

Cylindrical and spherical dust acoustic solitary waves in adiabatically hot dusty plasmas

The dust acoustic solitary waves (DASWs) in the presence of hot adiabatic dust in cylindrical and spherical geometries are investigated in an unmagnetized dusty plasma. The modified Korteweg–de Vries (mKdV) has been derived by using the reductive perturbation technique. The numerical solutions of the mKdV equation have been presented in both the geometries for hot dust plasmas. It is found that the amplitude of the dust acoustic wave (DAW) increases with the increase of dust temperature in both the geometries. However, the hot dust has more effect on DASW in spherical geometry as compared to the cylindrical case. These results might be very useful to explain the salient features of multidimensional DAWs for space and laboratory plasmas.

Energy loss of charged projectiles in dusty plasmas

The analytical and numerical results for the slowing down of two heavy projectile ions passing through a multicomponent dusty plasma are presented. Within the linear dielectric approach, the electrostatic potential and the stopping power of the two projectiles are computed for different values of KD (the normalized effective wave number) and R (the separation between the two projectiles) retaining two-ion-correlation effects. The enhancement in the energy loss is observed, and it is compared with that of a single ion projectile case. These results are useful to explain the crystallization of dust grains in astrophysical and laboratory plasmas.

Planar and nonplanar ion acoustic shock waves in relativistic degenerate astrophysical electron-positron-ion plasmas

We have studied the propagation of ion acoustic shock waves involving planar and non-planar geometries in an unmagnetized plasma, whose constituents are non-degenerate ultra-cold ions, relativistically degenerate electrons, and positrons. By using the reductive perturbation technique, Korteweg–deVries Burger and modified Korteweg–deVries Burger equations are derived. It is shown that only compressive shock waves can propagate in such a plasma system. The effects of geometry, the ion kinematic viscosity, and the positron concentration are examined on the ion acoustic shock potential and electric field profiles. It is found that the properties of ion acoustic shock waves in a non-planar geometry significantly differ from those in planar geometry. The present study has relevance to the dense plasmas, produced in laboratory (e.g., super-intense laser-dense matter experiments) and in dense astrophysical objects.

Planar and nonplanar dust acoustic solitary waves in electron–positron–ion–dust plasmas

Planar and nonplanar dust acoustic (DA) solitary waves are studied in an unmagnetized plasma consisting of electrons, positrons, ions and dust species. This is done by deriving the modified Kortweg–de Vries (mKdV) equation under the small amplitude perturbation expansion method. It is found that in the presence of positrons, DA hump-like solitary waves may also exist under suitable conditions. It is also observed that the positron concentration and the ratio of ion-to-electron temperature significantly modify the propagation characteristics of DA solitary waves. The range of plasma parameters for which we obtain hump-like solitons are found numerically. The present investigation may have relevance in both laboratory and astrophysical plasmas.

Propagation and stability of quantum dust-ion-acoustic shock waves in planar and nonplanar geometry

Dust-ion-acoustic (DIA) shock waves are studied in an unmagnetized quantum plasma consisting of electrons, ions, and dust by employing the quantum hydrodynamic (QHD) model. In this context, a Korteweg–deVries–Burger (KdVB) equation is derived by employing the small amplitude perturbation expansion method. The dissipation is introduced by taking into account the kinematic viscosity among the plasma constituents. It is found that the strength of the quantum DIA shock wave is maximum for spherical, intermediate for cylindrical, and minimum for the planar geometry. The effects of quantum Bohm potential, dust concentration, and kinematic viscosity on the quantum DIA shock structure are also investigated. The temporal evolution of DIA KdV solitons and Burger shocks are also studied by putting the dissipative and dispersive coefficients equal to zero, respectively. The effects of the quantum Bohm potential on the stability of the DIA shock is also investigated. The present investigation may be beneficial to unde...

Planar and cylindrical magnetosonic solitary and shock waves in dissipative, hot electron-positron-ion plasma

Planar and cylindrical magnetosonic solitary and shock structures are studied in a hot and dissipative plasma consisting of electrons, positrons, and ions. By employing the reductive perturbative method, a modified Korteweg-de Vries Burgers (mKdVB) equation is derived in the limit of low frequency and long wavelength by taking into account viscous dissipation of the three species. The effects of variation of various plasma parameters on the profiles of planar and cylindrical solitary and shock structures are discussed. In the limit, when certain terms of the mKdVB equation are small enough to be treated as perturbation, analytical solutions are obtained and compared with the corresponding numerical ones.