Gurudas Mandal

Nonplanar Ion Acoustic Solitary Waves in Electron-Positron-Ion Plasma With Warm Ions, and Electron and Positron Following

Cylindrical and spherical modified Korteweg-de Vries equations are derived for ion-acoustic solitary waves (IASWs) in an unmagnetized, collisionless electron-positron-ion plasma consisting of warm ion fluid and q-nonextensive distributed electrons and positrons by using standard reductive perturbation method. The effects of nonplanar geometry, nonextensivity of electrons and positrons, and other plasma parameters on nonlinear dynamics of cylindrical and spherical IASWs are studied numerically. Numerical results indicate that the amplitude of the soliton is large in spherical geometry in comparison with cylindrical geometry, and both the electron and positron nonextensive parameter has a significant effect on the structure of the nonplanar IASWs.

q

Abstract Considering the flat rotation curves as input and treating the matter content in the galactic halo region as quark matter, we have found out a background spacetime metric for the region of the galactic halo. We obtain fairly general conditions that ensure that gravity in the halo region is attractive. We also investigate the stability of circular orbits, along with a different role for quark matter. Bag-model quark matter meeting these conditions therefore provides a suitable model for dark matter.

-Nonextensive Velocity Distribution

The nonlinear propagation of dust-ion-acoustic (DIA) waves in a dusty electronegative plasma (consisting of inertialess electrons, nonthermal positive ions, inertial negative ions, and extremely massive charge fluctuating dust) has been investigated by employing the reductive perturbation technique. It has been shown that the effects of nonthermal ions and dust charge fluctuation (associated with Maxwellian electrons and nonthermal positive ions) have significantly modified the basic features of nonlinear DIA waves. The results of this paper would be useful in understanding the basic nonlinear feature of DIA wave propagation in laboratory and space dusty electronegative plasmas.

Quark matter as dark matter in modeling galactic halo

The nonlinear propagation of the dust-acoustic (DA) waves in a dusty plasma consisting of Boltzmann-distributed electrons and ions, and mobile charge fluctuating positive dust has been investigated by employing the reductive perturbation method. It has been shown that the dust charge fluctuation is a source of dissipation and is responsible for the formation of the DA shock waves in such a dusty plasma. The basic features of such DA shock waves have been identified. The basic features of the DA shock waves predicted in this investigation should be useful in understanding the properties of localized waves in some space dusty plasmas.

Effects of Nonthermal Ions on Dust-Ion-Acoustic Shock Waves in a Dusty Electronegative Plasma

The nonlinear propagation of dust-acoustic (DA) waves in an unmagnetized dusty plasma consisting of nonthermal electrons, vortex-like (trapped) distributed ions and mobile negative dust have been investigated by employing the reductive perturbation technique. The effects of nonthermal electrons and trapped ions are found to modify the properties of the DA solitary waves.

Dust-Acoustic Shock Waves in a Dusty Plasma With Charge Fluctuating Positive Dust

Abstract The nonlinear propagation and interaction of dust acoustic multi-solitons in a four component dusty plasma consisting of negatively and positively charged cold dust fluids, non-thermal electrons, and ions were investigated. By employing reductive perturbation technique (RPT), we obtained Korteweged–de Vries (KdV) equation for our system. With the help of Hirota’s bilinear method, we derived two-soliton and three-soliton solutions of the KdV equation. Phase shifts of two solitons and three solitons after collision are discussed. It was observed that the parameters α, β, β1, μe, μi, and σ play a significant role in the formation of two-soliton and three-soliton solutions. The effect of the parameter β1 on the profiles of two soliton and three soliton is shown in detail.

Nonlinear propagation of dust-acoustic waves in an unmagnetized dusty plasma with nonthermal electron and vortex-like ion distribution

The nonlinear propagation of dust-acoustic (DA) waves in a dusty plasma consisting of Boltzmann-distributed ions, vortex-like distributed electrons and mo- bile charge fluctuating positive dust has been investigated by employing the re- ductive perturbation method. The effects of dust grain charge fluctuation and the vortex-like electron distribution are found to modify the properties of the DA solitary waves significantly. The implications of these results for some space and astrophysical dusty plasma systems are briefly mentioned.

Overtaking Collision and Phase Shifts of Dust Acoustic Multi-Solitons in a Four Component Dusty Plasma with Nonthermal Electrons

The behavior of electromagnetic (EM) waves in a relativistic plasma is investigated. The governing equations of such dynamical plasma system are derived from the basic fluid model equations, and the vector and electrostatic potential are analyzed using Maxwells equations. A system of first-order, ordinary but nonlinear differential equations, is obtained from the two coupled second-order differential equations. Numerical results are found using the fourth order Runge-Kutta method. It is seen that EM shock waves are emerged for subsonic case, and on the other hand, periodic oscillatory solution as well as asymptotically stable state is obtained for supersonic case. The present investigation is important to extrapolate in different plasma backgrounds, like laboratory and astroplasma environments, viz., in laboratory biomedicine, biophysics, genetic engineering, laboratory astrophysics, and at different stages of stellar evolution.

Effects of vortex-like (trapped) electron distribution on non-linear dust-acoustic waves with positive dust charge fluctuation

Abstract A four-component dusty plasma consisting of electrons, ions, and negatively as well as positively charged dust grains has been considered. Shock waves may exist in such a four-component dusty plasma. The basic characteristics of shock waves have been theoretically investigated by employing reductive perturbation technique (RPT). It is found that negative as well as positive shock potentials are present in such dusty plasma. The present results may be useful for understanding the existence of nonlinear potential structures that are observed in different regions of space (viz. cometary tails, lower and upper mesosphere, Jupiter’s magnetosphere, interstellar media, etc).