Inertial Cold Electrons Research Articles

Modulational instability of electron-acoustic waves in magnetized plasma in presence of excess superthermal electrons

Modulational instability of finite amplitude electron-acoustic waves along external magnetic field is investigated in plasma composed of inertial cold electrons, hot inertialess superthermal electrons and stationary ions. Reductive perturbation technique is used to derive the three-dimensional nonlinear Schrodinger equation which governs the slow modulation of electron acoustic wave packets. Accounting for effects of hot electron to cold electron number density ratio (α), normalized electron-cyclotron frequency (ω c ) as well as the electron superthermal parameter (κ e ) new regimes for modulational instability of electron acoustic waves are obtained and analyzed. The presence of superthermal electrons modifies conditions for modulational instability to occur, as well as associated threshold and growth rate. Concentration of superthermal electrons (i.e., the deviation from a Maxwellian electron distribution) may control or even suppress modulational instability. In contrast to one-dimensional unmagnetized plasmas, instability growth rate is shown to suppress increasing values of k.

Modulational instability of electron-acoustic waves in plasmas with superthermal electrons

The propagation of electron-acoustic waves (EAWs) in plasmas composed of inertial cold electrons, hot superthermal electrons, and stationary ions is investigated. By means of the reduction perturbation technique, a nonlinear Schrödinger equation is derived and the modulation instability of EAW is analyzed, where the superthermal parameter is found to be of significant importance. It is shown that the presence of superthermal electrons enhances the critical wave number of the modulational instability of EAWs. Besides, due to the presence of the superthermal electrons, EAWs are stable on a vaster region. Moreover, the modulational instability growth rate is lower for a larger population of superthermal electrons. Further, it is shown that increasing values of the relative density ratio α = ne0/nc0 shifts the instability domain to lower values of wave number k.

Modulational instability of electron-acoustic waves in a plasma with a q-nonextensive electron velocity distribution

The amplitude modulation of electron-acoustic waves (EAWs) propagating in space plasmas whose constituents are inertial cold electrons, hot nonextensive q-distributed electrons, and stationary ions is presented theoretically. The nonlinear Schrödinger equation (NLSE) which governs the modulational instability of the EAWs is obtained using reductive perturbation method (RPM). The presence of the hot nonextensive q-distributed electrons is shown to influence the modulational instability of the waves. Further, the nondimensional parameter α = n e 0 / n c 0 , which is the equilibrium density ratio of the hot to cold electron component, is shown to play a vital role in the formation of both bright and dark solitons.

Electrostatic solitary waves in the presence of excess superthermal electrons: modulational instability and envelope soliton modes

The nonlinear dynamics of electrostatic solitary waves in the form of localized modulated wavepackets is investigated from first principles. Electron-acoustic (EA) excitations are considered in a two-electron plasma, via a fluid formulation. The plasma, assumed to be collisionless and uniform (unmagnetized), is composed of two types of electrons (inertial cold electrons and inertialess kappa-distributed superthermal electrons) and stationary ions. By making use of a multiscale perturbation technique, a nonlinear Schrödinger equation is derived for the modulated envelope, relying on which the occurrence of modulational instability (MI) is investigated in detail. Stationary profile localized EA excitations may exist, in the form of bright solitons (envelope pulses) or dark envelopes (voids). The presence of superthermal electrons modifies the conditions for MI to occur, as well as the associated threshold and growth rate. The concentration of superthermal electrons (i.e., the deviation from a Maxwellian electron distribution) may control or even suppress MI. Furthermore, superthermality affects the characteristics of solitary envelope structures, both qualitatively (supporting one or the other type, for different κ) and quantitatively, changing their characteristics (width, amplitude). The stability of bright and dark-type nonlinear structures is confirmed by numerical simulations.

Nonlinear electron-acoustic waves in quantum plasma

The nonlinear wave structure of electron-acoustic waves (EAWs) is investigated in a three component unmagnetized dense quantum plasma consisting of two distinct groups of electrons (one inertial cold electron, and other inertialess hot electrons) and immobile ions. By employing one dimensional quantum hydrodynamic model and standard reductive perturbation technique, a Korteweg–de-Vries equation governing the dynamics of EAWs is derived. Both compressive and rarefactive solitons along with periodical potential structures are found to exist for various ranges of dimensionless quantum parameter H. The quantum mechanical effects are also examined numerically on the profiles of the amplitude and the width of electron-acoustic solitary waves. It is observed that both the amplitude and the width of electron-acoustic solitary waves are significantly affected by the parameter H. The relevance of the present investigation to the astrophysical ultradense plasmas is also discussed.

Oblique modulation of electron-acoustic waves in a Fermi electron-ion plasma

The oblique modulational instability (MI) of electron-acoustic waves (EAWs) in a quantum plasma whose components are two distinct groups of electrons (one inertial cold electrons and other inertialess hot electrons) and immobile ions is investigated, by using a quantum hydrodynamic model. The analysis is carried out through the derivation of the nonlinear Schrödinger equation for the modulated EAW packets. The effects of obliqueness, the quantum diffraction (H), and the equilibrium density ratio of the cold to hot electron component (δ) on the MI of EAWs are numerically examined. At quantum scales, these parameters are found to significantly modify the MI domain in the plane of wave number and the angle (θ) between the modulation and the propagation direction. The relevance of our results in astrophysical environments, as well as in intense laser-solid density plasma interaction experiments is discussed.

Electron-acoustic solitary waves in dense quantum electron-ion plasmas

A quantum hydrodynamic (QHD) model is used to investigate the propagation characteristics of nonlinear electron-acoustic solitary waves (EASWs) in a dense quantum plasma whose constituents are two groups of electrons: one inertial cold electrons and other inertialess hot electrons, and the stationary ions which form the neutralizing background. By using the standard reductive perturbation technique, a Kadomtsev-Petviashvili (KP) equation, which governs the dynamics of EASWs, is derived in both spherical and cylindrical geometry. The effects of cold electrons and the density correlations due to quantum fluctuations on the profiles of the amplitudes and widths of the solitary structures are examined numerically. The nondimensional parameter δ=nc0∕nh0, which is the equilibrium density ratio of the cold to hot electron component, is shown to play a vital role in the formation of both bright and dark solitons. It is also found that the angular dependence of the physical quantities and the presence of cold electrons in a quantum plasma lead to the coexistence of some new interesting novel solitary structures quite distinctive from the classical ones.

Electron-acoustic plasma waves: oblique modulation and envelope solitons.

Theoretical and numerical studies are presented of the amplitude modulation of electron-acoustic waves (EAWs) propagating in space plasmas whose constituents are inertial cold electrons, Boltzmann distributed hot electrons, and stationary ions. Perturbations oblique to the carrier EAW propagation direction have been considered. The stability analysis, based on a nonlinear Schrödinger equation, reveals that the EAW may become unstable; the stability criteria depend on the angle theta between the modulation and propagation directions. Different types of localized EA excitations are shown to exist.