Md. Sahadat Alam | Jahangirnagar University (original) (raw)
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Papers by Md. Sahadat Alam
Positron acoustic shock waves (PASWs) in an unmagnetized four-component plasma system consisting ... more Positron acoustic shock waves (PASWs) in an unmagnetized four-component plasma system consisting of a cold mobile viscous positron fluid, hot positrons and electrons following the nonthermal distributions of Cairns et al. [Geophys. Res. Lett. 22, 2709], and immobile positive ions are studied both analytically and numerically. The well-known reductive perturbation method is used to derive the Burgers equation. The basic features of the PASWs are significantly modified by the effects of the kinematic viscosity, the nonthermal electrons and hot positrons, the ratio of the electron temperature to the hot positron temperature σ, and the ratio of the hot positron (electron) number density to the cold positron number density μ1 (μ2). The importance of our results to various astrophysical and laboratory plasmas are concisely discussed.
The basic properties of dust-ion-acoustic (DIA) shock waves in an unmagnetized dusty plasma (cont... more The basic properties of dust-ion-acoustic (DIA) shock waves in an unmagnetized dusty plasma (containing inertial ions, kappa distributed electrons with two distinct temperatures, and negatively charged immobile dust grains) are investigated both numerically and analytically. The hydrodynamic equation for inertial ions has been used to derive the Burgers equation. The effects of superthermal bi-kappa electrons and ion kinematic viscosity, which are found to modify the basic features of DIA shock waves significantly, are briefly discussed.
A rigorous theoretical investigation has been performed on the propagation of cylindrical and sph... more A rigorous theoretical investigation has been performed on the propagation of cylindrical and spherical Gardner solitons (GSs) associated with dust-ion acoustic (DIA) waves in a dusty plasma consisting of inertial ions, negatively charged immobile dust, and two populations of kappa distributed electrons having two distinct temperatures. The well known reductive perturbation method has been used to derive the mod ified Gardner (mG) equation. The basic features (amplitude, width, polarity, etc.) of nonplanar DIA modi fied Gardner solitons (mGSs) have been thoroughly examined by the numerical analysis of the mG equation. It has been found that the characteristics of the nonplanar DIA mGSs significantly differ from those of planar ones. It has been also observed that kappa distributed electrons with two distinct temperatures significantly modify the basic properties of the DIA solitary waves and that the plasma system under consideration sup ports both compressive and rarefactive DIA mGSs. The present investigation should play an important role for understanding localized electrostatic disturbances in space and laboratory dusty plasmas where stationary negatively charged dust, inertial ions, and superthermal electrons with two distinct temperatures are omni present ingredients.
Dust-ion-acoustic (DIA) waves in an unmagnetized dusty plasma system consisting of inertial ions,... more Dust-ion-acoustic (DIA) waves in an unmagnetized dusty plasma system consisting of inertial ions, negatively charged immobile dust, and superthermal (kappa distributed) electrons with two distinct temperatures are investigated both numerically and analytically by deriving Korteweg-de Vries (K-dV), modified K-dV (mK-dV), and Gardner equations along with its double layers (DLs) solutions using the reductive perturbation technique. The basic features of the DIA Gardner solitons (GSs) as well as DLs are studied, and an analytical comparison among K-dV, mK-dV, and GSs are also observed. The parametric regimes for the existence of both the positive as well as negative SWs and negative DLs are obtained. It is observed that superthermal electrons with two distinct temperatures significantly affect on the basic properties of the DIA solitary waves and DLs; and depending on the parameter μ c (the critical value of relative electron number density μ e1 ), the DIA K-dV and Gardner solitons exhibit both compressive and rarefactive structures, whereas the mK-dV solitons support only compressive structures and DLs support only the rarefactive structures. The present investigation can be very effective for understanding and studying various astrophysical plasma environments (viz. Saturn magnetosphere, pulsar magnetosphere, etc.).
A theoretical investigation has been made on positron-acoustic (PA) Gardner solitons (GSs) and do... more A theoretical investigation has been made on positron-acoustic (PA) Gardner solitons (GSs) and double layers (DLs) in four-component plasma system consisting of immobile positive ions, mobile cold positrons, nonthermal hot positrons, and nonthermal hot electrons. The reductive perturbation method has been used to derive Korteweg-de Vries (K-dV), modified K-dV (mK-dV), and Gardner equations. The basic features (viz. amplitude, polarity, speed, etc.) of the PA GSs as well as PA DLs are examined. The analytical comparison among K-dV solitons, mK-dV solitons, and GSs are also made. It has been identified that the amplitude, polarity, speed, thickness of such PA solitons and DLs are significantly modified due to the presence of nonthermal distributed hot electrons and hot positrons. The results of our investigation should be useful for understanding various interstellar space plasma environments (viz. ionosphere, lower part of magnetosphere, auroral acceleration regions, supernovas, pulsar environments, cluster explosions, active galactic nuclei, etc.). a considering superthermal (kappa distributed) electrons and positrons El-Tantawy et al. [24] examined the IA SWs and DLs in electron-positron-ion-dust (e-p-i-d) plasmas. Chatterjee et al. [25] studied nonlinear propagation of IA shock waves in an unmagnetized plasma system, in which both electrons and positrons following nonthermal distribution. Recently, nonlinear structures associated with positron-acoustic (PA) waves in e-p-i plasmas have received a great attention in understanding the localized electrostatic disturbances in space plasmas, and a number of attempts have already been done on the nonlinear propagation of PA waves [3, 26-29]. PA waves are basically acoustic-type waves, in which the inertia is provided by the cold positron mass, and the restoring force is provided by the thermal pressure of hot positrons. Tribeche et al. [3] investigated the PA SWs in a four-component plasma system consisting of cold positrons, immobile positive ions, and Boltzmann distributed electrons and hot positrons. One year later, Tribeche [27] examined the small amplitude PA DLs considering the same species in e-p-i plasmas. By using the Poincaré-Lighthill-Kuo method, El-Shamy et al. analyzed the head-on collision between two PA SWs in e-p-i space plasmas considering the same plasma model as well as the model of Tribeche [3, 27]. During the last decades, the formation of GSs and DLs [30-38] has been a topic of great interest.
A theoretical investigation has been performed on the nonlinear propagation of nonplanar (cylindr... more A theoretical investigation has been performed on the nonlinear propagation of nonplanar (cylindrical and spherical) Gardner solitons (GSs) associated with the positron-acoustic (PA) waves in a four component plasma system consisting of nonthermal distributed electrons and hot positrons, mobile cold positrons, and immobile positive ions. The well-known reductive perturbation method has been employed to derive the modified Gardner (MG) equation. The basic features (viz. amplitude, polarity, speed, etc.) of nonplanar PA Gardner solitons (GSs) have been examined by the numerical analysis of the MG equation. It has been observed that the properties of the PA GSs in a nonplanar geometry differ from those in a planar geometry. It has been also investigated that the presence of nonthermal (Cairns distributed) electrons and hot positrons significantly modify the amplitude, polarity, speed, and thickness of such PA GSs. The results of our investigation should play an important role in understanding various interstellar space plasma environments as well as laboratory plasmas.
The basic properties of nonplanar (viz. cylindrical and spherical) dust-ion-acoustic (DIA) shock ... more The basic properties of nonplanar (viz. cylindrical and spherical) dust-ion-acoustic (DIA) shock waves in an unmagnetized dusty plasma system [consisting of inertial ions, negatively charged immobile dust, and superthermal electrons with two distinct temperatures] are investigated by employing the reductive perturbation method. The modified Burgers equation is derived and is numerically analyzed in order to examine the basic properties of DIA shock structures. The effects of nonplanar geometry, electron superthermality, and ion kinematic viscosity on the basic features of DIA shock waves are discussed. It is found that the properties of the cylindrical and spherical DIA shock waves in dusty plasmas with two-temperature superthermal electrons significantly differ from those of one-dimensional planar shocks. The implications of our results in space plasmas [viz. star formation, supernovae explosion, solar wind, pulsar magnetosphere, Saturn's outer magnetosphere (R ∼ 13−18 R S , where R S is the radius of Saturn), Saturn's inner magnetosphere (R <9 R S , etc.)] and laboratory plasmas (viz. laser-induced implosion, capsule implosion, shock tube, etc.), where superthermal electrons with two distinct temperatures occurs, are briefly discussed.
in an unmagnetized four-component plasma (containing hot electrons and positrons following the q-... more in an unmagnetized four-component plasma (containing hot electrons and positrons following the q-nonextensive distribution, cold mobile viscous electron fluid, and immobile positive ions) are studied in nonplanar (cylindrical and spherical) geometry. With the help of the reductive perturbation method, the modified Burgers equation is derived. Analytically, the effects of nonplanar geometry, nonextensivity, relative number density and temperature ratios, and cold electron kinematic viscosity on the basic properties (viz. amplitude, width, speed, etc.) of EASWs are discussed. It is examined that the EASWs in nonplanar geometry significantly differ from those in planar geometry. The results of this investigation can be helpful in understanding the nonlinear features of EASWs in various astrophysical plasmas.
Books by Md. Sahadat Alam
Positron acoustic shock waves (PASWs) in an unmagnetized four-component plasma system consisting ... more Positron acoustic shock waves (PASWs) in an unmagnetized four-component plasma system consisting of a cold mobile viscous positron fluid, hot positrons and electrons following the nonthermal distributions of Cairns et al. [Geophys. Res. Lett. 22, 2709], and immobile positive ions are studied both analytically and numerically. The well-known reductive perturbation method is used to derive the Burgers equation. The basic features of the PASWs are significantly modified by the effects of the kinematic viscosity, the nonthermal electrons and hot positrons, the ratio of the electron temperature to the hot positron temperature σ, and the ratio of the hot positron (electron) number density to the cold positron number density μ1 (μ2). The importance of our results to various astrophysical and laboratory plasmas are concisely discussed.
The basic properties of dust-ion-acoustic (DIA) shock waves in an unmagnetized dusty plasma (cont... more The basic properties of dust-ion-acoustic (DIA) shock waves in an unmagnetized dusty plasma (containing inertial ions, kappa distributed electrons with two distinct temperatures, and negatively charged immobile dust grains) are investigated both numerically and analytically. The hydrodynamic equation for inertial ions has been used to derive the Burgers equation. The effects of superthermal bi-kappa electrons and ion kinematic viscosity, which are found to modify the basic features of DIA shock waves significantly, are briefly discussed.
A rigorous theoretical investigation has been performed on the propagation of cylindrical and sph... more A rigorous theoretical investigation has been performed on the propagation of cylindrical and spherical Gardner solitons (GSs) associated with dust-ion acoustic (DIA) waves in a dusty plasma consisting of inertial ions, negatively charged immobile dust, and two populations of kappa distributed electrons having two distinct temperatures. The well known reductive perturbation method has been used to derive the mod ified Gardner (mG) equation. The basic features (amplitude, width, polarity, etc.) of nonplanar DIA modi fied Gardner solitons (mGSs) have been thoroughly examined by the numerical analysis of the mG equation. It has been found that the characteristics of the nonplanar DIA mGSs significantly differ from those of planar ones. It has been also observed that kappa distributed electrons with two distinct temperatures significantly modify the basic properties of the DIA solitary waves and that the plasma system under consideration sup ports both compressive and rarefactive DIA mGSs. The present investigation should play an important role for understanding localized electrostatic disturbances in space and laboratory dusty plasmas where stationary negatively charged dust, inertial ions, and superthermal electrons with two distinct temperatures are omni present ingredients.
Dust-ion-acoustic (DIA) waves in an unmagnetized dusty plasma system consisting of inertial ions,... more Dust-ion-acoustic (DIA) waves in an unmagnetized dusty plasma system consisting of inertial ions, negatively charged immobile dust, and superthermal (kappa distributed) electrons with two distinct temperatures are investigated both numerically and analytically by deriving Korteweg-de Vries (K-dV), modified K-dV (mK-dV), and Gardner equations along with its double layers (DLs) solutions using the reductive perturbation technique. The basic features of the DIA Gardner solitons (GSs) as well as DLs are studied, and an analytical comparison among K-dV, mK-dV, and GSs are also observed. The parametric regimes for the existence of both the positive as well as negative SWs and negative DLs are obtained. It is observed that superthermal electrons with two distinct temperatures significantly affect on the basic properties of the DIA solitary waves and DLs; and depending on the parameter μ c (the critical value of relative electron number density μ e1 ), the DIA K-dV and Gardner solitons exhibit both compressive and rarefactive structures, whereas the mK-dV solitons support only compressive structures and DLs support only the rarefactive structures. The present investigation can be very effective for understanding and studying various astrophysical plasma environments (viz. Saturn magnetosphere, pulsar magnetosphere, etc.).
A theoretical investigation has been made on positron-acoustic (PA) Gardner solitons (GSs) and do... more A theoretical investigation has been made on positron-acoustic (PA) Gardner solitons (GSs) and double layers (DLs) in four-component plasma system consisting of immobile positive ions, mobile cold positrons, nonthermal hot positrons, and nonthermal hot electrons. The reductive perturbation method has been used to derive Korteweg-de Vries (K-dV), modified K-dV (mK-dV), and Gardner equations. The basic features (viz. amplitude, polarity, speed, etc.) of the PA GSs as well as PA DLs are examined. The analytical comparison among K-dV solitons, mK-dV solitons, and GSs are also made. It has been identified that the amplitude, polarity, speed, thickness of such PA solitons and DLs are significantly modified due to the presence of nonthermal distributed hot electrons and hot positrons. The results of our investigation should be useful for understanding various interstellar space plasma environments (viz. ionosphere, lower part of magnetosphere, auroral acceleration regions, supernovas, pulsar environments, cluster explosions, active galactic nuclei, etc.). a considering superthermal (kappa distributed) electrons and positrons El-Tantawy et al. [24] examined the IA SWs and DLs in electron-positron-ion-dust (e-p-i-d) plasmas. Chatterjee et al. [25] studied nonlinear propagation of IA shock waves in an unmagnetized plasma system, in which both electrons and positrons following nonthermal distribution. Recently, nonlinear structures associated with positron-acoustic (PA) waves in e-p-i plasmas have received a great attention in understanding the localized electrostatic disturbances in space plasmas, and a number of attempts have already been done on the nonlinear propagation of PA waves [3, 26-29]. PA waves are basically acoustic-type waves, in which the inertia is provided by the cold positron mass, and the restoring force is provided by the thermal pressure of hot positrons. Tribeche et al. [3] investigated the PA SWs in a four-component plasma system consisting of cold positrons, immobile positive ions, and Boltzmann distributed electrons and hot positrons. One year later, Tribeche [27] examined the small amplitude PA DLs considering the same species in e-p-i plasmas. By using the Poincaré-Lighthill-Kuo method, El-Shamy et al. analyzed the head-on collision between two PA SWs in e-p-i space plasmas considering the same plasma model as well as the model of Tribeche [3, 27]. During the last decades, the formation of GSs and DLs [30-38] has been a topic of great interest.
A theoretical investigation has been performed on the nonlinear propagation of nonplanar (cylindr... more A theoretical investigation has been performed on the nonlinear propagation of nonplanar (cylindrical and spherical) Gardner solitons (GSs) associated with the positron-acoustic (PA) waves in a four component plasma system consisting of nonthermal distributed electrons and hot positrons, mobile cold positrons, and immobile positive ions. The well-known reductive perturbation method has been employed to derive the modified Gardner (MG) equation. The basic features (viz. amplitude, polarity, speed, etc.) of nonplanar PA Gardner solitons (GSs) have been examined by the numerical analysis of the MG equation. It has been observed that the properties of the PA GSs in a nonplanar geometry differ from those in a planar geometry. It has been also investigated that the presence of nonthermal (Cairns distributed) electrons and hot positrons significantly modify the amplitude, polarity, speed, and thickness of such PA GSs. The results of our investigation should play an important role in understanding various interstellar space plasma environments as well as laboratory plasmas.
The basic properties of nonplanar (viz. cylindrical and spherical) dust-ion-acoustic (DIA) shock ... more The basic properties of nonplanar (viz. cylindrical and spherical) dust-ion-acoustic (DIA) shock waves in an unmagnetized dusty plasma system [consisting of inertial ions, negatively charged immobile dust, and superthermal electrons with two distinct temperatures] are investigated by employing the reductive perturbation method. The modified Burgers equation is derived and is numerically analyzed in order to examine the basic properties of DIA shock structures. The effects of nonplanar geometry, electron superthermality, and ion kinematic viscosity on the basic features of DIA shock waves are discussed. It is found that the properties of the cylindrical and spherical DIA shock waves in dusty plasmas with two-temperature superthermal electrons significantly differ from those of one-dimensional planar shocks. The implications of our results in space plasmas [viz. star formation, supernovae explosion, solar wind, pulsar magnetosphere, Saturn's outer magnetosphere (R ∼ 13−18 R S , where R S is the radius of Saturn), Saturn's inner magnetosphere (R <9 R S , etc.)] and laboratory plasmas (viz. laser-induced implosion, capsule implosion, shock tube, etc.), where superthermal electrons with two distinct temperatures occurs, are briefly discussed.
in an unmagnetized four-component plasma (containing hot electrons and positrons following the q-... more in an unmagnetized four-component plasma (containing hot electrons and positrons following the q-nonextensive distribution, cold mobile viscous electron fluid, and immobile positive ions) are studied in nonplanar (cylindrical and spherical) geometry. With the help of the reductive perturbation method, the modified Burgers equation is derived. Analytically, the effects of nonplanar geometry, nonextensivity, relative number density and temperature ratios, and cold electron kinematic viscosity on the basic properties (viz. amplitude, width, speed, etc.) of EASWs are discussed. It is examined that the EASWs in nonplanar geometry significantly differ from those in planar geometry. The results of this investigation can be helpful in understanding the nonlinear features of EASWs in various astrophysical plasmas.