Dense Magnetoplasma Research Articles

Negative energy dust acoustic waves evolution in a dense magnetized quantum Thomas–Fermi plasma

Propagation of nonlinear waves in the magnetized quantum Thomas–Fermi dense plasma is analyzed. The Zakharov–Kuznetsov–Burgers equation is derived by using the theory of reductive perturbation. The exact solution contains both solitary and shock terms. Also, it is shown that rarefactive waves propagate in most cases. Both the associated electric field and the wave energy have been derived. The effects of dust and electrons temperature, dust density, magnetic field magnitude, and direction besides the effect of the kinematic viscosity on the amplitude, width, and energy of the formed waves are discussed. It is shown that the negative energy wave is formed and its value is enhanced due to the increase of the kinematic viscosity and the ambient magnetic field which lead to an increase in the instability. The present results are helpful in controlling the stabilization of confined Thomas–Fermi dense magnetoplasma that are found in white dwarfs and in the high-intensity laser-solid matter interaction experiments.

Features of Turbulence Excited by Pulsed High-Frequency Pump in a Magnetoplasma

Turbulence developed in a magnetoplasma modified by a high-power high-frequency pulse fed to a loop antenna is discovered and studied on the large-scale KROT plasma device. Turbulence is manifested in the excitation of the electron density and magnetic field pulsations, deep self-modulation of the pump wave, and modulation of probe waves passing through the modified plasma region. The space–time characteristics of turbulence are determined using correlated plasma density measurements by a pair of miniature microwave resonator probes and a magnetic probe. It is established that turbulence is excited only in the transparency band of the dense magnetoplasma to electromagnetic radiation: turbulent perturbations of the density and magnetic field exist during pumping at frequencies lower than the electron cyclotron frequency and are absent at pumping frequencies exceeding the electron cyclotron frequency.

Obliquely overtaking collisions of electrostatic N-soliton in the Thomas-Fermi dense magnetoplasma

Overtaking collision of unidirectional dust acoustic waves in the Thomas-Fermi dense magnetoplasma has been investigated. The system consists of classical negatively charged dust particles with degenerate electrons and ions. Nonlinear Korteweg-de Vries (KdV) equation that characterizing the dust acoustic solitons in such a plasma model is derived. The system admits only rarefactive solitary waves. Hirota's bilinear method is used to investigate the overtaking collision of two and three-soliton solutions. The exchange of energies due to the overtaking collisions is affected by physical parameters such as the electron equilibrium density, the dust temperature, and the obliquity angle. This causes the solitons behavior to be alternated. The amplitude, and width increase as the dust temperature and electron density decrease or when the dust density increases. The magnetic field affects only the soliton's width. The phase shifts are also affected by the system parameters. The current study is an attempt to illuminate the properties of N-soliton in Thomas-Fermi dense magnetoplasma that are applicable in compact astrophysical objects such as white dwarfs and high-intensity laser-solid matter interaction experiments.

Oblique interaction of electrostatic nonlinear structures in relativistically degenerate dense magnetoplasmas

AbstractWe have investigated the interaction of obliquely propagating ion acoustic solitary waves in a magnetoplasma with relativistically degenerate electrons. Using the quantum hydrodynamics model and by employing the extended Poincaré–Lighthill–Kuo technique, we have derived a set of Korteweg de Vries equations for two solitons. We have observed that the system under consideration allows the formation of only compressive solitons and their velocities remain in the sub‐acoustic limit. Furthermore, phase shifts of solitons as a result of their interaction have been calculated. The phase shifts have been observed to be dependent on the obliqueness and the physical parameters of plasma. It has also been noticed that phase shifts remain negative for the whole range of parameters generally found in white dwarf stars. We have observed that the phase shifts enhance with the enhancement in number density, however, the converse happens when the magnetic field is enhanced. It has also been observed that the phase shift is slightly greater for the solitons that are less oblique as compared to their more oblique counterparts. Furthermore, we have estimated the spatial scales of interaction of solitons using the parameters found in white dwarf stars.

Overtaking collisions of oblique isothermal ion‐acoustic multisolitons in ultra‐relativistic degenerate dense magnetoplasmas

AbstractOvertaking collisions of oblique isothermal ion‐acoustic multisolitons are studied in an ultra‐relativistic degenerate dense magnetoplasma, containing non‐degenerate inertial warm ions and ultra‐relativistic degenerate inertialess electrons and positrons. A non‐linear Korteweg‐de Vries (KdV) equation describing oblique isothermal ion‐acoustic solitons (OIIASs) in such a plasma model is derived. By applying Hirota's bilinear method (HBM), the overtaking collisions of oblique isothermal ion‐acoustic multisoliton solutions are investigated. An in‐depth discussion shows that the amplitude, the width, and the phase shift of isothermal ion‐acoustic multisolitons increase as the obliqueness and the chemical potential of electrons increase. The deviation of the trajectories decreases with increasing concentration of fermions and the ion cyclotron frequency. The present finding of this study is applicable in compact objects, such as white dwarfs and neutron stars, having degenerate ultra‐relativistic dense electrons and positrons.

Head on interaction of magnetoacoustic solitons in a spin-1/2 dense plasma with geometrical effects

The head on interaction due to two magnetoacoustic solitons is studied in a dense electron-ion magnetoplasma with geometrical and electron spin effects. For this purpose, the extended Poincaré-Lighthill-Kuo (PLK) technique and quantum two fluid equations are utilized to derive a set of nonplanar Korteweg–de Vries equations. The PLK method incorporates the post collision trajectories and the phase shifts encountered by the magnetoacoustic solitons after collision. The interaction is numerically analyzed by choosing some typical plasma parameters from compact astrophysical objects. It is observed that the spin-1/2 effects, statistical pressure, displacement current and geometry of the system significantly modify the phase shifts encountered by the solitons. It is noticed that the enhancement in the number density reduces the phase shift of the colliding solitons. Furthermore, the cylindrical geometry is observed to decrease phase shift by comparison with the planar geometry. The present investigation provides a deeper insight of head on collision caused by the magnetoacoustic solitons in dense magnetoplasmas.

Arbitrary Amplitude Oblique Electrostatic Solitary Waves in a Degenerate Cold Dusty Magnetoplasma

Linear and nonlinear properties of obliquely propagating waves are studied in a degenerate dense cold magnetoplasma, comprising of Thomas–Fermi distributed electrons and ions as well as non-degenerate negatively charged dust particulates. By using the plane wave approximation, a linear dispersion relation for the dust-cyclotron (DC) and dust-acoustic (DA) waves is derived and analyzed numerically. For fully nonlinear waves, a Sagdeev pseudopotential theory is employed to derive an energy-balance equation and the soliton existence domain depending upon the dust concentration $(h)$ , obliqueness $(L_{z})$ , and Mach number $(M)$ . Numerical analysis reveals that the parameter $h$ enhances the domain for allowed Mach numbers, i.e., $M_{1} and therefore favoring the solitary excitations, where $M_{1}$ and $M_{2}$ are the lower and upper Mach numbers, respectively. In addition, the dust concentration significantly reduces the amplitude and the profile sharpness of the solitary pulses. Similarly, variations in the obliqueness parameter and the Mach numbers modify the wave characteristics. This paper is important for understanding the nonlinear properties of electrostatic excitations in degenerate dusty magnetoplasma, relevant to white dwarfs (WDs), namely $GD56,\,\,GD29-38,\,\,GD362$ , and $WD2115-560$ , being termed as the DUSTY DAZ WDs.

Magnetoacoustic shocks with geometrical effects in spin−12 dense plasmas

The propagation characteristics of magnetoacoustic shock waves are investigated in an electron-ion dense magnetoplasma that accounts for spin−12 electrons and geometrical effects within the framework of a two-fluid quantum magnetohydrodynamic model. For this purpose, we have employed the reductive perturbation technique and derived small-amplitude planar Korteweg de Vries Burgers (KdVB) and cylindrical KdVB equations. Numerically, cylindrical KdVB equations are analyzed by choosing the plasma parameters consistent with compact astrophysical systems. It is observed that the density, magnetic field, and viscosity are the parameters that ascertain significant modifications in the structure and propagation of magnetoacoustic shock waves. The amplitude of the shock wave becomes larger in the case of cylindrical geometry and propagates faster than that of planar shock waves. Furthermore, the results are compared with analytical solutions in the limit of earlier times to show an excellent agreement of the results. However, the magnetization energy is found to mitigate the amplitude of shock structures in a dense magnetoplasma where quantum spin effects cannot be ignored.

Parametric instabilities in a quantum magnetoplasma with electron exchange-correlations

Relying on the density functional theory, we have examined the impact of electron exchange-correlations on the nonlinear dispersion relations and associated parametric instabilities induced by nonlinear couplings of high-frequency quantum upper-hybrid waves (QUHWs) with different low-frequency waves, like quantum lower-hybrid waves (QLHWs), quantum ion-cyclotron waves (QICWs), and quantum Alfvén waves (QAWs) in a dense quantum magnetoplasma. For theoretical description of waves, we make use of quantum hydrodynamic equations to account for the electron exchange-correlation and Bohm potentials, strongly dependent on the density fluctuations. At quantum scales, nonlinear dispersion equations are derived for QUHWs, QICWs, QLHWs, and QAWs and then Fourier transformed for obtaining the nonlinear dispersion relations and growth rates involving the three wave decay and modulational instabilities in dense quantum magnetoplasmas. The relevance to nonlinear interactions due to high- and low-frequency waves in perspective of electron exchange-correlations is highlighted.

Modulational instability of ion-acoustic waves in magnetoplasma with pressure of relativistic electrons

In this research, the modulation of a weakly three-dimensional electrostatic ion-acoustic wave (IAW) is studied in dense magnetoplasma consisting of relativistic degenerate inertialess electrons and nondegenerate inertial thermal ions. It is assumed that the degeneracy pressure law for electrons follows the Chandrasekhar equation of state. The standard reductive perturbation theory has been applied to obtain the corresponding three-dimensional nonlinear Schrodinger equation, where the nonlinearity is in balance with the dispersive terms. This equation governs the dynamics and shows the slow modulation of the IAWs. This equation also been influenced not only by the external magnetic field but also by the usual plasma parameters. The numerical results indicate that new instability regimes arise when we consider the relativistic parameter ( μe), the ion to electron temperature ratio (σi), and the normalized ion cyclotron frequency (ωci) which though cannot be observed in the unmagnetized case can considerably modify the profiles of the envelope magneto acoustic solitons. Also, some significant explicit critical frequencies are obtained, which permit us to consider new regimes different from the usual unmagnetized plasma for propagation of IAWs in the magnetoplasma, which may exist in space or astrophysics.

Solitary waves in a degenerate relativistic plasma with ionic pressure anisotropy and electron trapping effects

The dynamics of obliquely propagating ion-acoustic (IA) waves in the presence of ionic pressure anisotropy and electron trapping effects is studied in a dense magnetoplasma, containing degenerate relativistic trapped electrons and dynamical (classical) ions. By using the plane wave solution, a modified linear dispersion relation for IA waves is derived and analyzed with different limiting cases and various plasma parameters both analytically and numerically. For nonlinear analysis, a reductive perturbation technique is employed to obtain a Zakharov-Kuznetsov equation involving the weakly nonlinear IA excitations. It is shown that the electron thermal correction and ionic pressure anisotropy strongly modify the wave amplitudes and width attributed to weakly nonlinear IA waves. The stability criterion for stable/unstable solitary pulses is also discussed with variations of angle (β) and temperature ratio (σ). A reduction and domain splitting of unstable excitations into sub-domains with stable and unstable potential pulses are pointed out for electron temperature ratio in the range of 0.01 < σ < 0.3 for degenerate relativistic trapped electrons. Moreover, the ionic pressure anisotropy also considerably affects the stability of solitary potentials in the non-relativistic and ultra-relativistic regimes. The obtained results might be useful for understanding the nonlinear dynamics and propagation characteristics of waves in superdense plasmas, in the environments of white dwarfs and neutron stars, where the electron thermal and ionic pressure anisotropy effects cannot be ignored.

Drift vortices in inhomogeneous collisional dusty magnetoplasma**Project supported by the National Natural Science Foundation of China (Grant Nos. 11365017, 11465015, 11405110, 11305031, and 11404214) and the Technology Landing Project of the Education Department of Jiangxi Province of China (Grant No. KJLD13086).

For the sake of investigating the drift coherent vortex structure in an inhomogeneous dense dusty magnetoplasma, using the quantum hydrodynamic model a nonlinear controlling equation is deduced when the collision effect is considered. New vortex solutions of the electrostatic potential are obtained by a special transformation method, and three evolutive cases of monopolar vortex chains with spatial and temporal distribution are analyzed by representative parameters. It is found that the collision frequency, particle density, drift velocity, dust charge number, electron Fermi wavelength, quantum correction, and quantum parameter are all influencing factors of the vortex evolution. Compared to the uniform dusty system, the vortex solutions of the inhomogeneous system present richer spatial evolution and physical meaning. These results may explain corresponding vortex phenomena and support beneficial references for the dense dusty plasma atmosphere.

Nonlinear propagation of electrostatic travelling waves in degenerate dense magnetoplasmas

The electrostatic travelling wave structures have been investigated in degenerate dense magnetoplasmas consisting of relativistic degenerate inertialess electrons and positrons, as well as nondegenerate inertial cold ions. The well known reductive perturbation method has been applied in obtaining the nonlinear Zakharov-Kuznetsov equation. The formation of the electrostatic solitary waves and periodic travelling waves is carried out by the bifurcation theory of planar dynamical systems. The results demonstrate that the nonlinear electrostatic travelling waves strongly depend on the concentration of positrons, the ion cyclotron frequency, and the direction cosines of the wave vector. The obtained results here may be useful for better understanding of the structure of nonlinear electrostatic travelling wave in dense plasmas, such as the interior of massive white dwarfs.

Dust acoustic waves in collisional uniform dense magnetoplasma**Project supported by the National Natural Science Foundation of China (Grant Nos. 11365017, 11465015, 11305031, 11405110, and 11275123) and the Technology Landing Project of the Education Department of Jiangxi Province of China (Grant No. KJLD13086).

In order to study the characteristics of dust acoustic waves in a uniform dense dusty magnetoplasma system, a nonlinear dynamical equation is deduced using the quantum hydrodynamic model to account for dust–neutral collisions. The linear dispersion relation indicates that the scale lengths of the system are revised by the quantum parameter, and that the wave motion decays gradually leading the system to a stable state eventually. The variations of the dispersion frequency with the dust concentration, collision frequency, and magnetic field strength are discussed. For the coherent nonlinear dust acoustic waves, new analytic solutions are obtained, and it is found that big shock waves and wide explosive waves may be easily produced in the background of high dusty density, strong magnetic field, and weak collision. The relevance of the obtained results is referred to dense dusty astrophysical circumstances.

Modulationally stable envelope solitons in astrophysical magnetoplasmas with degenerate relativistic electrons

The formation and propagation characteristics of small-amplitude magnetoacoustic dark/grey solitons are investigated in a semi relativistic degenerate magnetoplasma whose constituents are electrons and singly ionized positive ions. For this purpose, the electrons are assumed to follow the degeneracy pressure law through the Chandrasekhar equation of state, while the inertial cold ions are taken as non-degenerate and magnetized. By solving the one-fluid quantum magnetohydrodynamic (QMHD) model with the aid of a reductive perturbation technique, a nonlinear Schrödinger (NLS) equation is derived for weakly nonlinear envelope magnetoacoustic solitons. The NLS equation admits the existence of stable excitations, e.g. dark and grey solitons for which the condition $P/Q<0$ holds. Numerical results reveal that the variation of plasma number density, magnetic field strength, relativistic parameter $({\it\eta}_{e0})$ and the quantum parameter $(H)$ significantly modify the profiles of the envelope magnetoacoustic solitons. The present results are important to understanding of the nonlinear dynamics of magnetoacoustic solitons in astrophysical dense magnetoplasmas (viz., white dwarfs, magnetars, neutron stars, etc.), where the relativistic degeneracy effects play a vital role in collective interactions.

Obliquely propagating quasi one dimensional electrostatic solitary structures in dense magnetoplasmas with trapped electrons

In the present investigation, we have studied the linear and nonlinear propagation of electrostatic waves in a dense magnetoplasma with trapped electrons. Using the small amplitude approximation, formation of solitary structures has been studied both for fully and partially degenerate plasmas. The theoretical results obtained have been analyzed numerically for the parameters typically found in white dwarfs. The present work may be beneficial to understand the propagation of solitary structures with weak transverse perturbation with special reference to white dwarf asteroseismology.

Modulation of drift-wave envelopes in a nonuniform quantum magnetoplasma

We study the amplitude modulation of low-frequency, long-wavelength electrostatic drift-wave envelopes in a nonuniform quantum magnetoplasma consisting of cold ions and degenerate electrons. The effects of tunneling associated with the quantum Bohm potential and the Fermi pressure for nonrelativistic degenerate electrons, as well as the equilibrium density and magnetic field inhomogeneities are taken into account. Starting from a set of quantum magnetohydrodynamic equations, we derive a nonlinear Schrödinger equation (NLSE) that governs the dynamics of the modulated quantum drift-wave packets. The NLSE is used to study the modulational instability (MI) of a Stoke's wave train to a small plane wave perturbation. It is shown that the quantum tunneling effect as well as the scale length of inhomogeneity plays crucial roles for the MI of the drift-wave packets. Thus, the latter can propagate in the form of bright and dark envelope solitons or as drift-wave rogons in degenerate dense magnetoplasmas.

Symbolic Computation on Soliton Solutions for Variable-coefficient Quantum Zakharov-Kuznetsov Equation in Magnetized Dense Plasmas

Abstract The (3+1)-dimensional quantum Zakharov-Kuznetsov equations with variable coefficients have the applications to nonlinear ion-acoustic waves in dense magnetoplasmas. Via a simplified bilinear method and symbolic computation, we construct the multiple solitary wave solutions, analyze the elastic collisions with the constant and variable coefficients, and observe that solitons no longer keep rectilinear propagation and display different shapes because of the inhomogeneities of media. Then, a dense magnetoplasma consisting of electrons and singly charged ions is considered. The basic set of quantum hydrodynamic is reduced to the quantum Zakharov-Kuznetsov equation by using the reductive perturbation technique. Parametric analysis is carried out in order to illustrate that the soliton amplitude, width and velocity are affected by the quantum diffraction and obliqueness effect. Furthermore, propagation characteristics and interaction behaviors of the solitons are also discussed through the graphical analysis and the characteristic-line method.

Dynamic behavior of the quantum Zakharov-Kuznetsov equations in dense quantum magnetoplasmas

Quantum Zakharov-Kuznetsov (qZK) equation is found in a dense quantum magnetoplasma. Via the spectral analysis, we investigate the Hamiltonian and periodicity of the qZK equation. Using the Hirota method, we obtain the bilinear forms and N-soliton solutions. Asymptotic analysis on the two-soliton solutions shows that the soliton interaction is elastic. Figures are plotted to reveal the propagation characteristics and interaction between the two solitons. We find that the one soliton has a single peak and its amplitude is positively related to He, while the two solitons are parallel when He < 2, otherwise, the one soliton has two peaks and the two solitons interact with each other. Hereby, He is proportional to the ratio of the strength of magnetic field to the electronic Fermi temperature. External periodic force on the qZK equation yields the chaotic motions. Through some phase projections, the process from a sequence of the quasi-period doubling to chaos can be observed. The chaotic behavior is observed since the power spectra are calculated, and the quasi-period doubling states of perturbed qZK equation are given. The final chaotic state of the perturbed qZK is obtained.

Three dimensional electrostatic solitary waves in a dense magnetoplasma with relativistically degenerate electrons

In this paper, small but finite amplitude electrostatic solitary waves in a relativistic degenerate magnetoplasma, consisting of relativistically degenerate electrons and non-degenerate cold ions, are investigated. The Zakharov-Kuznetsov equation is derived employing the reductive perturbation technique and its solitary wave solution is analyzed. It is shown that only compressive electrostatic solitary structures can propagate in such a degenerate plasma system. The effects of plasma number density, ion cyclotron frequency, and direction cosines on the profiles of ion acoustic solitary waves are investigated and discussed at length. The relevance of the present investigation vis-a-vis pulsating white dwarfs is also pointed out.