Nazia Batool

Nonlinear structures of drift waves in pair-ion-electron plasmas

The Korteweg–de Vries–Burgers equation is derived for drift waves in a partially ionized nonuniform pair-ion-electron (PIE) plasma. The nonlinearity appears due to electron temperature gradient. The analytical solutions in the form of solitons, monotonic shocks, and oscillatory shocks have been obtained. The numerical calculations have also been presented for PIE plasmas of fullerene and hydrogen for illustration keeping in view the recent experiments. This work can be useful for future experimental investigations.

Toroidal ion-temperature-gradient driven vortices in an inhomogeneous magnetoplasma with non-Maxwellian electrons

Nonlinear equations which govern the dynamics of low-frequency toroidal ion-temperature-gradient driven modes (i.e., ω≪ωci, where ωci is the ion gyro-frequency) are derived in the presence of equilibrium density, temperature, and magnetic field gradients. In the nonlinear case, solutions in the form of dipolar vortices and vortex street are presented for a plasma comprising of Maxwellian ions and nonthermal electrons that are embedded in an external magnetic field. By using Braginskiis transport equations for the Maxwellian ions and Kappa distributed electrons, the coupled mode equations for the system under consideration are derived. The results have been applied in Tokamak plasmas, and it has been observed that the scale lengths over which the nonlinear vortex structures form get modified in the presence of Kappa distributed electrons. The present study is also applicable to tokamaks and stellarators where non-Maxwellian population has been observed in resonant frequency heating, electron cyclotron hea...

The effects of nonthermal electron distributions on ion-temperature-gradient driven drift-wave instabilities in electron-ion plasma

The effects of nonthermal electron distributions on electrostatic ion-temperature-gradient (ITG) driven drift-wave instabilities in the presence of equilibrium density, temperature, and magnetic field gradients are investigated here. By using Braginskii’s transport equations for ions and Cairns as well as Kappa distribution for electrons, the coupled mode equations are derived. The modified ITG driven modes are derived, and it is found both analytically as well as numerically that the nonthermal distribution of electrons significantly modify the real frequencies as well as the growth rate of the ITG driven drift wave instability. The growth rate of ion-temperature-gradient driven instability is found to be maximum for Cairns, intermediate for Kappa, and minimum for the Maxwellian distributed electron case. The results of present investigation might be helpful to understand several wave phenomena in space and laboratory plasmas in the presence of nonthermal electrons.

Interaction of fast magnetoacoustic solitons in dense plasmas

One dimensional propagation of fast magnetoacoustic solitary waves in dense plasmas with degenerate electrons is investigated in this paper in the small amplitude limit. In this regard, Korteweg deVries equation is derived and discussed using the plasma parameters that are typically found in white dwarf stars. The interaction of fast magnetoacoustic solitons is explored by using the Hirota bilinear formalism, which admits multi soliton solutions. It is observed that the values of the propagation vectors determine the interaction of solitary waves. It is further noted that the amplitude of the respective solitary waves remain unchanged after the interaction; however, they do experience a phase shift.

Exact solution of CKP equation and formation and interaction of two solitons in pair-ion-electron plasma

In the present investigation, cylindrical Kadomstev-Petviashvili (CKP) equation is derived in pair-ion-electron plasmas to study the propagation and interaction of two solitons. Using a novel gauge transformation, two soliton solutions of CKP equation are found analytically by using Hirotas method and to the best of our knowledge have been used in plasma physics for the first time. Interestingly, it is observed that unlike the planar Kadomstev-Petviashvili (KP) equation, the CKP equation admits horseshoe-like solitary structures. Another non-trivial feature of CKP solitary solution is that the interaction parameter gets modified by the plasma parameters contrary to the one obtained for Korteweg–de Vries equation. The importance of the present investigation to understand the formation and interaction of solitons in laboratory produced pair plasmas is also highlighted.

Interaction of solitons for obliquely propagating magnetoacoustic waves in stellar atmosphere

We study here the nonlinear oblique propagation of magnetoacoustic waves in dense plasmas with degenerate electrons by deriving Kadomtsev-Petviashvili (KP) equation for small but finite amplitude perturbations. The two soliton interaction has been studied by finding the solution of the KP equation using the Hirota bilinear formalism. For illustrative purposes, we have used the plasma parameters typically found in white dwarf stars for both the fast and slow modes of magnetoacoustic waves. It has been observed that the soliton interaction in the fast and slow modes is strongly influenced by the predominant and weak dispersive coefficients of the KP equation. The single soliton behavior has also been explained for the fast and slow magnetoacoustic modes.

Cylindrically confined pair-ion-electron and pair-ion plasmas having axial sheared flow and radial gradients

The linear and nonlinear dynamics of pair-ion (PI) and pair-ion-electron plasmas (PIE) have been investigated in a cylindrical geometry with a sheared plasma flow along the axial direction having radial dependence. The coupled linear dispersion relation of low frequency electrostatic waves has been presented taking into account the Guassian profile of density and linear gradient of sheared flow. It is pointed out that the quasi-neutral cold inhomogeneous pure pair ion plasma supports only the obliquely propagating convective cell mode. The linear dispersion relation of this mode has been solved using boundary conditions. The nonlinear structures in the form of vortices formed by different waves have been discussed in PI and PIE plasmas.

Shear flow-driven electrostatic instabilities in low density and low temperature pair-ion plasmas with and without electrons

The shear flow-driven electrostatic instabilities are investigated in ideal low density, low temperature pair-ion-electron and pure pair-ion plasmas in several different cases, including homogeneous and inhomogeneous density effects. In uniform pair-ion-electron plasma, when the shear flow is of the order of the acoustic speed, the purely growing D’Angelo mode can give rise to electrostatic fields. In the case of an inhomogeneous plasma, the drift wave becomes unstable. The presence of negative ions, however, reduces the growth rate. If the positive and negative ions are not in thermal equilibrium with each other, then the shear flow also gives rise to an electrostatic instability in pure pair-ion plasma.

Formation of dipolar vortices and vortex streets due to nonlinearly interacting ion-temperature-gradient-driven modes in dense magnetoplasmas

Nonlinear equations which govern the dynamics of low-frequency (ω ⪡ ωci, where ω is the perturbation frequency of the wave and ωci is the ion gyro-frequency), ion-temperature-gradient-driven modes in the presence of equilibrium density, temperature and magnetic field gradients are derived. New set of nonlinear equations are derived. In the nonlinear case, new types of solutions in the form of dipolar vortices and vortex streets are found to exist in dense quantum plasma. These structures are found to be formed on very short spatial scales.

Ion-temperature-gradient-driven modes in bi-ion magnetoplasma

The toroidal ion-temperature-gradient (ITG)-driven electrostatic drift waves are investigated for bi-ion plasmas with equilibrium density, temperature and magnetic field gradients. Using Braginskiis transport equations for the ions and Boltzmann distributed electrons, the mode coupling equations are derived. New ITG-driven modes are shown to exist. The results of the present study should be helpful to understand several wave phenomena in space and tokamak plasmas.