Browsing by Author "Shah, M. G."

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Compressive and rarefactive ion-acoustic solitons in a magnetized quantum plasma
(Springer, 2016-04-06) Hosen, B.; Shah, M. G.; Hossen, M. R.; Mamun, A. A.
Compressive and rarefactive ion-acoustic solitary waves (IASWs) in a magnetized, collisionless, three-component, dense plasma system have been carried out. The plasma system is assumed to be composed of non-degenerate inertial ions, degenerate electrons and immobile positively charged heavy ions. The magnetized Korteweg-de Vries (K-dV) and modified K-dV (mK-dV) equations are derived by adopting reductive perturbation method to study the basic characteristics of IASWs. It is seen that the effects of degenerate pressure, number density of electrons, inertial ions, and positively charged static heavy ions significantly modify the fundamental features of IASWs. It is also found that the magnetic field (obliqueness) has a significant contribution on the characteristics of IASWs. The implication of our results in some space and laboratory plasma situations are concisely discussed. Full Text Link: https://doi.org/10.1140/epjp/i2016-16081-y
Electroacoustic Waves in a Collision-free Magnetized Super thermal Bi-ion Plasma
(Plasma Physics Reports, Springer, 2019) Sarker, M.; Hossen, M. R.; Shah, M. G.; Hosen, B.; . Mamun, A. A.
The electroacoustic waves, particularly ion-acoustic waves (IAWs), and their expansion in the medium of a magnetized collision-free plasma system has been investigated theoretically. The plasma system is assumed to be composed of both positively and negatively charged mobile ion species and kappa-distributed hot electron species. In the nonlinear perturbation regime, the magnetized Korteweg–de Vries (KdV) and magnetized modified KdV (mKdV) equations are derived by using reductive perturbation method. The prime features (i.e., amplitude, phase speed, width, etc.) of the IAWs are studied precisely by analyzing the stationary solitary wave solutions of the magnetized KdV and magnetized mKdV equations, respectively. It occurs that the basic properties of the IAWs are significantly modified in the presence of the excess super thermal hot electrons, obliqueness, and the plasma particle number densities, etc. It is also observed that, in case of magnetized KdV solitary waves, both compressive and rarefactive structures are formed, whereas only compressive structures are found for the magnetized mKdV solitary waves. The implication of our results in some space and laboratory plasma situations is concisely discussed.
Heavy Ion-Acoustic Solitary Waves and Double Layers in a Multi-Ion Plasma
(Springer, 2018-08-01) Shah, M. G.; Rahman, M. M.; Hossen, M. R.; Mamun, A. A.
The formation and propagation of small-amplitude heavy-ion-acoustic (HIA) solitary waves and double layers in an unmagnetized collisionless multicomponent plasma system consisting of superthermal electrons, Boltzmann distributed light ions, and adiabatic positively charged inertial heavy ions are theoretically investigated. The reductive perturbation technique is employed to derive the modified Korteweg–de Vries (mKdV) and standard Gardner (SG) equations. The solitary wave (SW) solution of mKdV and SG equations, as well as double layers (DLs) solution of SG equation, is studied for analysis of higher order nonlinearity. It is found that the plasma system under consideration supports positive and negative potential Gardner solitons, but only positive potential mKdV solitons. In addition, it is shown that, the basic properties of HIA mKdV and Gardner solitons and DLs (viz. polarity, amplitude, width, and phase speed) are incomparably influenced by the adiabaticity effect of heavy ions and the superthermality effect of electrons. The relevance of the present findings to the system of space plasmas, as well as to the system of researchers interest, is specified. Full Text Link: https://doi.org/10.1134/S1063780X18090131
Instability Analysis of Positron-Acoustic Waves in a Magnetized Multi-Species Plasma
(IOP Science, 2016-07-20) Hossen, M. A.; Shah, M. G.; Hossen, M. R.; Mamun, A. A.
The nonlinear propagation of electrostatic excitations and their multi-dimensional instability in a magnetized, degenerate electron-positron-ion (EPI) plasma system (containing inertial cold positrons, relativistic degenerate electrons and hot positrons, and negatively charged immobile heavy ions) are theoretically investigated. The reductive perturbation method is employed to derive the Zakharov–Kuznetsov equation which admits a localized solitary wave solution for small but finite amplitude limit, and the multi-dimensional instability of the positron acoustic solitary waves (PASWs) is studied by the small-k perturbation expansion method. It is found that the basic characteristics (viz. phase speed, amplitude, width) of the PASWs are significantly affected by the degree of obliqueness, relativistic degeneracy, and plasma particle number densities. The instability criterion and its growth rate, which are depending on the magnetic field and the propagation directions of both the PASWs, and their perturbation modes are discussed. The present analysis can be helpful in understanding the nonlinear phenomenon in dense astrophysical as well as space plasma systems, especially in pulsar environments. Full Text Link: https://doi.org/10.1088/0253-6102/67/4/458
Ion-Acoustic Solitary Waves and Double Layers in a Magnetized Degenerate Quantum Plasma
(IEEE Xplore, 2017-11-09) Hosen, B.; Shah, M. G.; Hossen, M. R.; Mamun, A. A.
The properties of ion-acoustic (IA) solitary waves (SWs) and double layers (DLs) in a four-component magnetized degenerate quantum plasma system (containing nondegenerate inertial light ion, both nonrelativistically and ultrarelativistically degenerate electrons and positrons, and immobile heavy ion) are theoretically investigated by the reductive perturbation method. The Korteweg-de Vries (K-dV), the modified K-dV, and the Gardner equations are derived to examine the basic features (viz. amplitude, speed, and width) of IA SWs and DLs. It is found that the effects of the ultrarelativistically degenerate electrons and positrons, stationary heavy ion, external magnetic field (obliqueness), and so on, significantly modify the basic features of the IA SWs and DLs. The basic features and the underlying physics of IA SWs and DLs, which are relevant to some astrophysical compact objects including white dwarfs and neutron stars, are pinpointed. Full Text Link: http://doi.org/10.1109/TPS.2017.2766167
Nonlinear propagation of positron-acoustic waves in a four component space plasma
(Cambridge University Press, 2015-08-04) Shah, M. G.; Hossen, M. R.; Mamun, A. A.
The nonlinear propagation of positron-acoustic waves (PAWs) in an unmagnetized, collisionless, four component, dense plasma system (containing non-relativistic inertial cold positrons, relativistic degenerate electron and hot positron fluids as well as positively charged immobile ions) has been investigated theoretically. The Korteweg–de Vries (K–dV), modified K–dV (mK–dV) and further mK–dV (fmK–dV) equations have been derived by using reductive perturbation technique. Their solitary wave solutions have been numerically analysed in order to understand the localized electrostatic disturbances. It is observed that the relativistic effect plays a pivotal role on the propagation of positron-acoustic solitary waves (PASW). It is also observed that the effects of degenerate pressure and the number density of inertial cold positrons, hot positrons, electrons and positively charged static ions significantly modify the fundamental features of PASW. The basic features and the underlying physics of PASW, which are relevant to some astrophysical compact objects (such as white dwarfs, neutron stars etc.), are concisely discussed. Full Text Link: https://doi.org/10.1017/S0022377815001014
Nonplanar Positron-Acoustic Shock Waves in Astrophysical Plasmas
(Springer, 2015-02-18) Shah, M. G.; Hossen, M. R.; Mamun, A. A.
The problem of nonlinear positron-acoustic shock waves (PASWs) in an unmagnetized, collisionless, dense plasma system (containing non-relativistic cold positrons, both non-relativistic and ultra-relativistic degenerate electrons, and hot positron fluids and positively charged static ions) is addressed. The combined effects of the non-relativistic and ultra-relativistic degenerate electron and hot positron fluids are organized in the study of the PASWs. By using the reductive perturbation method, modified Burgers equation is derived and numerically analyzed. For the non-relativistic limits in like manner for the ultra-relativistic limits, it is seen that the shock wave characteristics are modified significantly. The effects of kinematic viscosity, degenerate pressure, nonplanar geometries, and plasma particle number densities on the properties of PASWs are numerically analyzed. As time goes, PASWs propagating in cylindrical and spherical geometry are deformed. The fundamental features and the underlying physics of PASWs, which are concerned to some astrophysical compact objects (viz. neutron stars, white dwarfs, etc.), are concisely mentioned. Full Text Link: https://doi.org/10.1007/s13538-015-0304-4
Nonplanar solitons in a degenerate multi-species plasma
(Springer, 2015-05-06) Shah, M. G.; Mamun, A. A.; Hossen, M. R.
The nonlinear propagation of cylindrical and spherical positron-acoustic solitary waves (PASWs) in an unmagnetized, collisionless, relativistic, degenerate plasma system that consists of nonrelativistic inertial cold positrons, relativistic degenerate electron and hot positron fluids, and positively-charged immobile ions has been investigated theoretically. By using a reductive perturbation technique, we derive the Korteweg-de Vries (K-dV) equation. The solitary wave solution has been numerically analyzed to comprehend the localized electrostatic disturbances. We observed that the effects of the degenerate pressure, relativity, and the number densities of inertial cold positrons, hot positrons, electrons, and positively-charged static ions notably modify the fundamental features of the cylindrical and the spherical PASWs. The implications of our results for dense plasmas in astrophysical compact objects (e.g., non-rotating white dwarfs, neutron stars, etc.) are briefly discussed. Full Text Link: https://doi.org/10.3938/jkps.66.1239
Oblique Propagation of Electrostatic Waves in a Magnetized Electron-Positron-Ion Plasma in the Presence of Heavy Particles
(De Gruyter, 2018-04-06) Sarker, M.; Hossen, M. R.; Shah, M. G.; Hosen, B.; Mamun, A. A.
A theoretical investigation is carried out to understand the basic features of nonlinear propagation of heavy ion-acoustic (HIA) waves subjected to an external magnetic field in an electron-positron-ion plasma that consists of cold magnetized positively charged heavy ion fluids and superthermal distributed electrons and positrons. In the nonlinear regime, the Korteweg-de Vries (K-dV) and modified K-dV (mK-dV) equations describing the propagation of HIA waves are derived. The latter admits a solitary wave solution with both positive and negative potentials (for K-dV equation) and only positive potential (for mK-dV equation) in the weak amplitude limit. It is observed that the effects of external magnetic field (obliqueness), superthermal electrons and positrons, different plasma species concentration, heavy ion dynamics, and temperature ratio significantly modify the basic features of HIA solitary waves. The application of the results in a magnetized EPI plasma, which occurs in many astrophysical objects (e.g. pulsars, cluster explosions, and active galactic nuclei) is briefly discussed. Full Text Link: https://doi.org/10.1515/zna-2017-0419
Positron-Acoustic Shock Waves in a Degenerate Multi-Component Plasma
(IOP Science, 2014-11-06) Shah, M. G.; Hossen, M. R.; Sultana, S.; Mamun, A. A.
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. Full Text Link: https://doi.org/10.1088/0256-307X/32/8/085203
Properties of cylindrical and spherical heavy ion-acoustic solitary and shock structures in a multispecies plasma with superthermal electrons
(Springer, 2016-03-25) Shah, M. G.; Rahman, M. M.; Hossen, M. R.; Mamun, A. A.
A theoretical investigation on heavy ion-acoustic (HIA) solitary and shock structures has been accomplished in an unmagnetized multispecies plasma consisting of inertialess kappa-distributed superthermal electrons, Boltzmann light ions, and adiabatic positively charged inertial heavy ions. Using the reductive perturbation technique, the nonplanar (cylindrical and spherical) Kortewg–de Vries (KdV) and Burgers equations have been derived. The solitary and shock wave solutions of the KdV and Burgers equations, respectively, have been numerically analyzed. The effects of superthermality of electrons, adiabaticity of heavy ions, and nonplanar geometry, which noticeably modify the basic features (viz. polarity, amplitude, phase speed, etc.) of small but finite amplitude HIA solitary and shock structures, have been carefully investigated. The HIA solitary and shock structures in nonplanar geometry have been found to distinctly differ from those in planar geometry. Novel features of our present attempt may contribute to the physics of nonlinear electrostatic perturbation in astrophysical and laboratory plasmas. Full Text Link: https://doi.org/10.1134/S1063780X16020069
Relativistic Ion-Acoustic Solitary Waves in a Magnetized Pair Ion Dense Plasma with Nuclei of Heavy Elements
(Springer, 2018-08-01) Hosen, B.; Shah, M. G.; Hossen, M. R.; Mamun, A. A.
The propagation of ion-acoustic solitary waves (IASWs) in a magnetized collisionless degenerate plasma system for describing collective plasma oscillations in dense quantum plasmas with relativistically degenerate electrons, oppositely charged inertial ions, and positively charged immobile heavy elements is investigated theoretically. The perturbations of the magnetized quantum plasma are studied employing the reductive perturbation technique to derive the Korteweg–de Vries (KdV) and the modified KdV (mKdV) equations that admit solitary wave solutions. Chandrasekhar limits are used to investigate the degeneracy effects of interstellar compact objects through the equation of state for degenerate electrons in nonrelativistic and ultrarelativistic cases. The basic properties of small but finite-amplitude IASWs are modified significantly by the combined effects of the degenerate electron number density, pair ion number density, static heavy element number density, and magnetic field. It is found that the obliqueness affects both the amplitude and width of the solitary waves, whereas the other parameters mainly influence the width of the solitons. The results presented in this paper can be useful for future investigations of astrophysical multi-ion plasmas. Full Text Link: https://doi.org/10.1134/S1063780X18100045
Roles of Superthermal Electrons and Adiabatic Heavy Ions on Heavy-Ion-Acoustic Solitary and Shock Waves in a Multi-Component Plasma
(IOP Science, 2015-02-27) Shah, M. G.; Rahman, M. M.; Hossen, M. R.
Heavy-ion-acoustic (HIA) waves in an unmagnetized collisionless plasma system comprising superthermal electrons, Boltzmann distributed light ions, and adiabatic positively charged inertial heavy ions have been investigated both numerically and analytically. The well-known reductive perturbation method has been used to derive the Korteweg-de Vries (K-dV) and Burgers (BG) equations. The parametric regimes for the existence of both the positive and negative solitary and shock waves have been obtained. The effects of adiabaticity of heavy ions and superthermality of electrons, which are found to notably modify the fundamental features (viz. polarity, amplitude, phase speed, etc.) of HIA solitary and shock waves, are precisely studied. The results of our theoretical investigation can be applicable to understand the characteristics and basic nonlinear structures of HIA waves both in space and laboratory plasma situations. Full Text Link: https://doi.org/10.1088/0253-6102/64/2/208