S. Sultana

Oblique propagation of ion-acoustic solitary waves in a magnetized electron-positron-ion plasma

The properties of obliquely propagating ion-acoustic solitary waves in the presence of ambient magnetic field have been investigated theoretically in an electron-positron-ion nonthermal plasma. The plasma nonthermality is introduced via the q-nonextensive distribution of electrons and positrons. The Korteweg-de Vries (K-dV) and modified K-dV (mK-dV) equations are derived by adopting reductive perturbation method. The solution of K-dV and modified K-dV equation, which describes the solitary wave characteristics in the long wavelength limit, is obtained by steady state approach. It is seen that the electron and positron nonextensivity and external magnetic field (obliqueness) have significant effects on the characteristics of solitary waves. A critical value of nonextensivity is found for which solitary structures transit from positive to negative potential. The findings of this investigation may be used in understanding the wave propagation in laboratory and space plasmas where static external magnetic field is present.

Positron-Acoustic Shock Waves in a Degenerate Multi-Component Plasma

A theoretical investigation on the propagation of positron-acoustic shock waves (PASWs) in an unmagnetized, collisionless, dense plasma (containing non-relativistic inertial cold positrons, non-relativistic or ultra-relativistic degenerate electron and hot positron fluids and nondegenerate positively charged immobile ions) is carried out by employing the reductive perturbation method. The Burgers equation and its stationary shock wave solution are derived and numerically analyzed. It is observed that the relativistic effect (i.e., the presence of non/ultra-relativistic electrons and positrons) and the plasma particle number densities play vital roles in the propagation of PASWs. The implications of our results in space and interstellar compact objects including non-rotating white dwarfs, neutron stars, etc. are briefly discussed.

Oblique propagation of low frequency nonlinear waves in an electron depleted magnetized plasma with positive and negative dust

A rigorous theoretical investigation has been carried out to study the properties of obliquely propagating dust-acoustic (DA) waves in an electron depleted magnetized dusty plasma system containing nonextensive q-distributed ions and mobile positively charged, as well as negatively charged dust particles. The reductive perturbation technique is employed to derive the modified Korteweg-de Vries (mK-dV) equation to analyze solitary waves (SWs) and the standard Gardner (SG) equation to analyze SWs and double layers (DLs) solution. The basic features (viz., amplitude, polarity, speed, width, etc.) of the DA mK-dV SWs, SG SWs, and DLs are examined. The comparison between mK-dV SWs and SG SWs is also made. It is seen that the amplitude, polarity, speed, width of such DA SWs, and DLs are significantly modified by the presence of nonextensive ions, external magnetic field, and obliquity angle (the angle between the external magnetic field and wave propagation). The results of our present investigation may be usef...

Envelope solitons in three-component degenerate relativistic quantum plasmas

The criteria for the formation of envelope solitons and their basic features in a three-component degenerate relativistic quantum plasma (DRQP) system (containing relativistically degenerate electrons, non-degenerate inertial light nuclei, and stationary heavy nuclei) are theoretically investigated. The nonlinear Schrodinger equation is derived by employing the multi-scale perturbation technique. The envelope solitons are found to be associated with the modified ion-acoustic waves in which the inertia (restoring force) is provided by the mass density of light nuclei (degenerate pressure of cold electrons). The basic features of these envelope solitons, which are found to formed in such a DRQP system, and their modulational instability criteria (on the basis of the plasma parameters associated with the degenerate pressure of electrons, number densities of degenerate electrons, inertial light nuclei, and stationary heavy nuclei) are identified. The numerical simulations are also performed to confirm the sta...

Modulated heavy nucleus-acoustic waves and associated rogue waves in a degenerate relativistic quantum plasma system

A theoretical and numerical investigation has been carried out on amplitude modulated heavy nucleus-acoustic envelope solitons (HNAESs) in a degenerate relativistic quantum plasma (DRQP) system containing relativistically degenerate electrons and light nuclei, and non-degenerate mobile heavy nuclei. The cubic nonlinear Schrodinger equation, describing the nonlinear dynamics of the heavy nucleus-acoustic waves (HNAWs), is derived by employing a multi-scale perturbation technique. The dispersion relation for the HNAWs is derived, and the criteria for the occurrence of modulational instability of the HNAESs are analyzed. The localized structures (viz., envelope solitons and associated rogue waves) are found to be formed in the DRQP system under consideration. The basic features of the amplitude modulated HNAESs and associated rogue waves formed in realistic DRQP systems are briefly discussed.

Arbitrary amplitude nucleus-acoustic solitons in multi-ion quantum plasmas with relativistically degenerate electrons

A three component degenerate relativistic quantum plasma (consisting of relativistically degenerate electrons, nondegenerate inertial light nuclei, and stationary heavy nuclei) is considered to model the linear wave and also the electrostatic solitary waves in the light nuclei-scale length. A well-known normal mode analysis is employed to investigate the linear wave properties. A mechanical-motion analog (Sagdeev-type) pseudo-potential approach, which reveals the existence of large amplitude solitary excitations, is adopted to study the nonlinear wave properties. Only the positive potential solitary excitations are found to exist in the plasma medium under consideration. The basic properties of the arbitrary amplitude electrostatic acoustic modes in the light nuclei-scale length and their existence domain in terms of soliton speed (Mach number) are examined. The modifications of solitary wave characteristics and their existence domain with the variation of different key plasma configuration parameters (e....

Shear Alfvén Waves in a Magnetized Electron–Positron Plasma

A theoretical investigation of high-frequency shear Alfvén waves is made in a magnetized relativistic rotating electron–positron (e–p) plasma. The derivative nonlinear Schrödinger equation (DNSE) is derived by employing the reductive perturbation technique. A stationary solitary solution of DNSE is derived, which is used to analyze the basic properties (amplitude, width, etc.) of shear e–p Alfvén (SEPA) solitons. Different intrinsic plasma parameters (namely, positrons thermal energy to electrons thermal energy ratio and relativistic effects, etc.) are seen to influence the basic properties of SEPA waves significantly. It is found that the SEPAs have new features with high time and small length scales. The phase speed of the waves is seen to increase with the relativistic parameter while it decreases with the increase of positron-to-electron (p–e) thermal energy ratio. It is also observed that both the soliton’s amplitude and width increase with the increase of p–e thermal energy ratio, which are independent of rotational frequency. Our findings are useful to understand e–p plasma in the rotational astrophysical object.

Nonlinear Compressional Alfvén Waves in a Fully Relativistic Electron–Positron Plasma

A theoretical investigation has been carried out to study the nonlinear propagation of high-frequency electromagnetic (EM) waves in a magnetized relativistic rotating electron–positron plasma. The Korteweg-de Vries (K-dV) equation is derived by employing the reductive perturbation technique. The steady-state solution of K-dV equation is used to analyze the basic properties of small amplitude high-frequency compressional electron–positron Alfvén (CEPA) solitons. It is observed that opposite polarity electron–positron plasma medium under consideration supports the CEPA solitons having new features with time (fast) and length (small) scales. It is also found that both the amplitude and width of the solitons increase with the increase of positron thermal energy to electron thermal energy ratio which are independent of rotational frequency. The findings of this investigation may be used in understanding the nonlinear EM waves phenomena in space, rotating astrophysical plasmas, and laboratory plasmas.