Nonuniform Magnetized Plasma Research Articles

Terahertz wave propagation characteristics in SMM-based three-dimensional plasma fluid

During the return to the atmosphere of a hypersonic vehicle in adjacent space, a plasma sheath forms on the surface of the vehicle, which blocks normal electromagnetic communications. The ‘blackout’ phenomenon caused by plasma sheaths has received much attention. This paper focuses on the American RAM-C vehicle as the research object, and utilizes the fluid simulation software USim to numerically simulate the pressure, temperature, and electron density under different flight conditions, and based on the simulation results, selects the appropriate electron density and plasma collision frequency, introduces the terahertz (THz) wave, and adopts the scattering matrix method (SMM) to study the propagation characteristics of the vertically incident non-uniform magnetized plasma with the terahertz wave. Among other things, the transmission characteristics of terahertz waves in the plasma are affected by the flight altitude and flight angle of attack of the vehicle. The conclusions indicate that the transmissivity of terahertz wave transmission in plasma increases, and the reflectivity and absorptance decrease with increasing flight altitude and flight angle of attack. Under the condition of controlling other flight parameters unchanged, the plasma frequency and collision frequency decrease with the increase of flight altitude. The larger the flight angle of attack is, the larger the plasma frequency and collision frequency are. The electron density on the wall surface of the vehicle was also tested, and it was found that the lowest electron density was found at the tail end of the leeward surface. This study can provide some theoretical references for mitigating the ‘blackout’ phenomenon of re-entry vehicles.

Localization of electron modes in nonuniform helicon plasma

New guided electrostatic and electromagnetic modes propagating in a nonuniform magnetized plasma with plane geometry are presented. The modes may arise in a plasma with a region of strong inhomogeneity leading to a concentration of wave energy and, thus, a localization of the modes. These localized modes can only propagate if the density gradient is sufficiently strong, whereas they do not exist in weakly nonuniform plasma. The eigenfunctions and the spectrum of the modes are found. In detail, the properties of the modes are studied for particular profiles in the transitional layer between two uniform plane plasma regions.

Hamiltonian formulations of quasilinear theory for magnetized plasmas

Hamiltonian formulations of quasilinear theory are presented for the cases of uniform and nonuniform magnetized plasmas. First, the standard quasilinear theory of Kennel and Engelmann (Kennel, Phys. Fluids, 1966, 9, 2377) is reviewed and reinterpreted in terms of a general Hamiltonian formulation. Within this Hamiltonian representation, we present the transition from two-dimensional quasilinear diffusion in a spatially uniform magnetized background plasma to three-dimensional quasilinear diffusion in a spatially nonuniform magnetized background plasma based on our previous work (Brizard and Chan, Phys. Plasmas, 2001, 8, 4762–4771; Brizard and Chan, Phys. Plasmas, 2004, 11, 4220–4229). The resulting quasilinear theory for nonuniform magnetized plasmas yields a 3 × 3 diffusion tensor that naturally incorporates quasilinear radial diffusion as well as its synergistic connections to diffusion in two-dimensional invariant velocity space (e.g., energy and pitch angle).

Drifts effect on the ordinary plasma wave and the existence of new spin dependent electron drift in the spin quantum plasma

Using a separated spin evolution quantum hydrodynamic model, we have derived generalized formula for drift effects of electrons in the inhomogeneous and nonuniform magnetized spin quantum plasma. We report, for the first time, the appearance of new spin dependent drift along with grad-B drift and diamagnetic drift. These results can be used to study the drift effects on various waves and instabilities. To check the applicability of our results, we have derived the dispersion relation of ordinary-mode (O-mode) incorporating electron spin, gradient in density, and magnetic field. We have studied various new features due to electron spin, perpendicular spin drifts, and grad B on the propagation of O-mode. Numerical analysis is presented for the choice of laboratory plasma parameters.

Formation of a Charged Layer in a Bounded Non-Uniform Magnetized Plasma in RF Field

A model of plasma dynamics in the box of an ICRF (ion cyclotron radio-frequency) antenna without Faraday shield used for the plasma heating in tokamaks is proposed. Formation of a macroscopic layer of oscillating charge that plays a role of a shield is predicted. Relation to phenomena observed in a scrape-off layer plasma is discussed.

Theory of coupled resistive drift and resistive drift ballooning instabilities in fusion plasma

Drift wave instabilities (DWI) associated with the two-fluid dynamics seems to be responsible for anomalous transport in modern day tokamaks. Ballooning instabilities tend to exchange flux tubes of different pressure, resulting in convective transport. The micro-level turbulence (drift wave) is coupled with the macro-level (ballooning mode) dynamics in fusion experiments. The co-existence of DWI and drift ballooning instabilities (DBI) is discussed in this work using a four-field plasma model. The formulation preserves both the microscopic and macroscopic dynamics of plasma. To demonstrate the coupling, a new dispersion relation is derived to analyze stability of the coupled modes in a non-uniform magnetized plasma. Linear stability of coupled drift-ballooning and drift-acoustic modes have been explored. The two-fluid effect (micro-level influence) through diamagnetic drift frequency for electrons and curvature drift frequency on unstable modes are demonstrated.

Suppression of the Kelvin–Helmholtz instability due to polarization force in nonuniform magnetized sheared dusty plasmas

The Kelvin–Helmholtz (K–H) instability in a magnetized nonuniform velocity sheared dusty plasma is investigated accounting for the effects of dust polarization force due to inhomogeneity in background plasma number densities. A three-component fluid model for dusty plasma is formulated considering Boltzmann electron/ion fluids and flowing magnetized dust fluids whose dynamics are affected due to the presence of dust polarization force. A dispersion relation for the K–H instability is derived by applying normal mode analysis on the linearized perturbation equations of the system. It is found that the polarization parameter dependent dust acoustic mode significantly modifies the dispersion relation of the K–H instability. The critical shear required to excite the K–H instability (S > Scrit) decreases with an increase in the dust polarization parameter and dust cyclotron frequency. The growth rate of the K–H instability is observed to be suppressed due to the presence of the dust polarization parameter. The results have been discussed for experimental magnetized dusty plasmas, which shows that under considered parametric limits, one cannot ignore the presence of dust polarization force on the excitation of the K–H instability in dusty plasmas. The astrophysical consequences are also discussed in Saturn’s E-ring in the limiting case of varying dust grain size.

Analysis of transmission characteristics of THz waves magnetized at different angles in non-uniform magnetized plasma

When a hypersonic vehicle flies, it will have friction with the atmosphere, ionizing the surrounding air, and producing a plasma sheath containing a large number of free electrons. The plasma sheath will cause the electromagnetic wave to seriously attenuate, which will result in communication interruption and other problems. With the gradual realization of terahertz wave technology, its high penetrability and anti-interference performance provides an important way to solve the blackout problem. Thus, the using of the terahertz wave to solve the blackout problem encountered during vehicle reentry is of great significance to studying the transmission performance of terahertz wave in the plasma sheath. This article refers to the public data of the plasma sheath during the reentry of the RAM vehicle. Considering the asymmetry of the sheath density distribution, a double Gaussian distribution is used to simulate the longitudinal electron density distribution. Based on the SMM algorithm, the article uses the magnetization direction, electron density, external magnetic field strength, collision frequency of the non-uniformly magnetized plasma as variables, and their effects on left-hand and right-hand polarized terahertz wave under normal incidence are studied. The results show that these parameters have obvious effects on the transmission performance of terahertz wave in high-density plasma sheath. The right-hand polarized terahertz wave will produce a power absorption peak near the cyclotron frequency due to cyclotron resonance. Changing the magnetization angle in a certain direction will bring an opposite effect on the transmission rate to left-hand polarized and right-hand polarized terahertz wave. Reducing the magnetization intensity can avoid the absorption peak of the right-hand polarized wave by the plasma to a certain extent. Increasing the magnetization can increase the transmission power of the left-hand polarized wave to a certain extent. Moreover, reducing the collision frequency can narrow the absorption band of the right-hand polarized wave in the plasma and increase the transmission power of left-hand polarized wave. In general, the transmission performance of left-hand polarized terahertz wave in non-uniformly magnetized plasma is better than that of right-hand polarized terahertz wave. These results provide a theoretical basis for investigating the blackout phenomenon. The adjusting of these parameters studied in the article is expected to be able to alleviate the blackout problem to a certain extent.

Drift wave in strong collisional dusty magnetoplasma

The study about the wave mechanism of magnetized dusty plasmas has important value to related experiment, industrial processing and exploring celestial space. The linear and nonlinear fluctuation characteristics of the nonuniform magnetized dust plasma system are researched in this paper. For the homogeneous external magnetic field and the nonuniform environment with density and temperature gradients, a two-dimensional nonlinear dynamic magnetoplasma equation is derived considering the strong impact between dust and neutral particles. The linear dispersion relation is obtained by the linearized method. There are both the damping wave causing by strong collision and the harmonic wave by particle drift. Employing the typical numerical parameters for analysis, the results display that the quantum parameter modifies the system lengths; the real wave frequency is proportion to the drift frequency; the imaginary wave frequency has complex relationship with the collision frequency between dust and neutrals, and the collision of particles causes the dissipation effects to the system. Besides, the analytical solutions of drift shock wave and explosive wave are solved by function change method. The variation about the electrostatic potential with the main physical parameters is discussed in detail. It is shown that the strength of the electrostatic shock wave and the width of the explosive wave increase with increasing the dust density and magnetic field intensity, decrease with increasing the collision frequency, change with the drift velocity. When the space-time phase is small, the electrostatic potential changes quickly; once big enough, the potential tends to be stable value and reaches stable state eventually. Finally, the stability of the system is discussed. It is found that the dusty charge, quantum parameter, drift velocity all appear in the disturbed solution. All these results in the paper show that the strong collision effect, quantum effect, particle drift and magnetic field all play important role to the generation, evolution and stability of drift waves.

Bilinear plasma susceptibility of strongly non-uniform magnetized plasmas

The bilinear plasma susceptibility describing the nonlinear coupling of electromagnetic and two electrostatic waves in strongly non-uniform magnetized plasmas is derived using both the distribution function moments equations and the kinetic approach. The possibility of the drastic enhancement of nonlinear coupling leading to a decrease of the two-plasmon decay instability threshold in strongly inhomogeneous plasmas is demonstrated.

Electromagnetic Viscous-Resistive-Drift-Wave Instability in Burning Plasma

Drift wave instabilities (DWI) might be take a part for anomalous transport in modern day tokamaks due to contributions of edge turbulence and zonal flows. Experimentally, it is found that micro-level turbulence (associated with two-fluid dynamics) braced with macro-level (associated with single-fluid dynamics) magnetohydrodynamics-type processes. In this paper, additional two-fluid effect viz. ion viscosity on the electromagnetic (EM) linear resistive drift wave instability is analyzed by using a two-fluid MHD model. A modify dispersion relation for EM drift modes in a nonuniform magnetized plasma is derived, taken into account equilibrium pressure gradients, effect of finite ion-sound gyro-radius associated with electron–ion decoupling and viscous effect due to ions. The dispersion relation is then analyzed both analytically as well as numerically. It is shown, how additional two-fluid effects modify the growth rate for DWI in different regimes. The standard resistive drift-Alfven mode is reproduced in the cold ion case. Moreover, it is estimated that these effects provide the possibility of novel effects on EM instabilities in a nonuniform magnetized plasma. The results should be useful in the interpretation of EM fluctuations in nonuniform magneto-plasmas in which resistivity is a key element in calculations of dissipative drift instabilities.

Existence regimes for shocks in inhomogeneous magneto-plasmas having entropy

The finding of connection of plasma density and temperature with entropy gives an incitement to study different plasma models with respect to entropy. Nonlinear dissipative one- and two-dimensional structures (shocks) are investigated in nonuniform magnetized plasma with respect to entropy. The dissipation comes in the medium through ion-neutral collisions. The linear dispersion relation is derived. The Korteweg–deVries-Burgers and Kadomtsev-Petviashvili-Burgers equations are derived for nonlinear drift waves in 1-D and 2-D by employing the drift approximation. It is found that vd/u (vd is the diamagnetic drift velocity and u is the velocity of nonlinear structure) plays a significant role in the shock formation. It is also found that entropy has a significant effect on the strength of shocks. It is noticed that vd/u determines the rarefactive and compressive nature of the shocks. It is observed that upper and lower bounds exist for the shock velocity. It is also observed that the existing regimes for both one- and two-dimensional shocks for kappa distributed electrons are different from shocks with Cairns distributed electrons. Both rarefactive and compressive shocks are found for the 1-D drift waves with kappa distributed electrons. Interestingly, it is noticed that entropy enhances the strength of one- and two-dimensional shocks.

Study on the attenuation characteristic of terahertz wave through a non-uniform magnetized plasma

In this paper, the interaction between terahertz wave and a non-uniform magnetized plasma slab is investigated. The electric field distribution in non-uniform plasma is presented and used to calculate the attenuation of the electromagnetic wave through plasma. Several types of electron density profiles are proposed and discussed. Effects of different plasma parameters (electron density, collision frequency, plasma thickness) and magnetic field amplitudes on THz wave attenuation characteristic are investigated. The transmission ratios at several typical THz signal frequencies in both unmagnetized and magnetized plasma are presented as well. These simulation results are meaningful for the flight communication.

Effects of magnetized plasma on the propagation properties of obliquely incident THz waves

In this paper, the propagation of obliquely incident terahertz (THz) wave in a non-uniform magnetized plasma slab is investigated. The electron density and the collision frequency across the plasma are assumed to have a Gaussian profile. To deal with the non-uniform profile, the plasma slab is divided into a series of subslabs. For more accuracy, twice reflection between the interfaces of each subslab is considered, and the corresponding transmitted and reflected power are derived. Effects of collision frequency, magnetic field amplitude and incident angle on THz wave propagation characteristics are investigated. Specifically, the refraction angles in each subslab are presented. These simulation results are meaningful for the hypersonic flight communication.

Linear and Nonlinear Coupling of Electrostatic Drift and Acoustic Perturbations in a Nonuniform Bi-Ion Plasma with Non-Maxwellian Electrons

Linear and nonlinear coupling of drift and ion acoustic waves are studied in a nonuniform magnetized plasma comprising of Oxygen and Hydrogen ions with nonthermal distribution of electrons. It has been observed that different ratios of ion number densities and kappa and Cairns distributed electrons significantly modify the linear dispersion characteristics of coupled drift-ion acoustic waves. In the nonlinear regime, KdV (for pure drift waves) and KP (for coupled drift-ion acoustic waves) like equations have been derived to study the nonlinear evolution of drift solitary waves in one and two dimensions. The dependence of drift solitary structures on different ratios of ion number densities and nonthermal distribution of electrons has also been explored in detail. It has been found that the ratio of the diamagnetic drift velocity to the velocity of the nonlinear structure determines the existence regimes for the drift solitary waves. The present investigation may be beneficial to understand the formation of solitons in the ionospheric F-region.

Numerical evaluation of external magnetic effect on electromagnetic wave transmission through reentry plasma layer

Numerical study of electromagnetic (EM) wave transmission through the magnetized plasma layer is presented in this paper. The plasma parameters are derived from computational fluid dynamics simulation of the flow field around a blunt body flying at supersonic speed and serve as the background plasma condition in the numerical modeling for EM wave transmission. The EM wave is generated by our newly designed coaxial feed GPS patch antenna. The external magnetic field is applied and assumed to vary linearly as a function of wall distance. The effects of the external applied magnetic field and the plasma parameters on wave transmission are studied, and the results show that EM wave propagation in the non-uniformly magnetized plasma is a matter of impedance matching, and the EM wave transmission can be adjusted only when the proper strength of the magnetic field is applied.

Existence regimes for the formation of nonlinear dissipative structures in inhomogeneous magnetoplasmas with non-Maxwellian electrons

Nonlinear dissipative structures are studied in one and two dimensions in nonuniform magnetized plasmas with non-Maxwellian electrons. The dissipation is incorporated in the system through ion-neutral collisions. Employing the drift approximation, nonlinear drift waves are derived in 1D, whereas coupled drift-ion acoustic waves are derived in 2D in the weak nonlinearity limit. It is found that the ratio of the diamagnetic drift velocity to the velocity of nonlinear structure determines the nature (compressive or rarefactive) of the shock structure. The upper and lower bounds for velocity of the nonlinear shock structures are also found. It is noticed that the existence regimes for the drift shock waves in one and two dimensions for Cairns distributed electrons are very distinct from those with kappa distributed electrons. Interestingly, it is found that both compressive and rarefactive shock structures could be obtained for the one dimensional drift waves with kappa distributed electrons.

Effects of magnetic field on the interaction between terahertz wave and non-uniform plasma slab

In this paper, the interaction between terahertz electromagnetic wave and a non-uniform magnetized plasma slab is investigated. Different from most of the published literatures, the plasma employed in this work is inhomogeneous in both collision frequency and electron density. Profiles are introduced to describe the non-uniformity of the plasma slab. At the same time, magnetic field is applied to the background of the plasma slab. It came out with an interesting phenomenon that there would be a valley in the absorption band as the plasma's electromagnetic characteristic is affected by the magnetic field. In addition, the valley located just near the middle of the absorption peak. The cause of the valley's appearance is inferred in this paper. And the influences of the variables, such as magnetic field strength, electron density, and collision frequency, are discussed in detail. The objective of this work is also pointed out, such as the applications in flight communication, stealth, emissivity, plasma diagnose, and other areas of plasma.

Variational symplectic particle-in-cell simulation of nonlinear mode conversion from extraordinary waves to Bernstein waves

In this paper, the nonlinear mode conversion of extraordinary waves in nonuniform magnetized plasmas is studied using the variational symplectic particle-in-cell simulation. The accuracy of the nonlinear simulation is guaranteed by the long-term accuracy and conservativeness of the symplectic algorithm. The spectra of the electromagnetic wave, the evolution of the wave reflectivity, the energy deposition profile, and the parameter-dependent properties of radio-frequency waves during the nonlinear mode conversion are investigated. It is illustrated that nonlinear effects significantly modify the physics of the radio-frequency injection in magnetized plasmas. The evolutions of the radio-frequency wave reflectivity and the energy deposition are observed, as well as the self-interaction of the Bernstein waves and mode excitations. Even for waves with small magnitude, nonlinear effects can also become important after continuous wave injections, which are common in the realistic radio-frequency wave heating and current drive experiments.

Modified Zakharov–Kuznetsov equation for a non-uniform electron–positron–ion magnetoplasma with kappa-distributed electrons

We investigate the low-frequency (by comparison with the ion Larmor frequency) electrostatic solitary structures in a spatially non-uniform electron–positron–ion (e–p–i) magnetoplasma with non-Maxwellian electrons. A linear dispersion relation for the obliquely propagating ion acoustic drift wave is derived and it is shown that the non-Maxwellian electron population modifies the dispersion characteristics of the wave under consideration. We also carry out a nonlinear analysis and derive the modified Zakharov–Kuznetsov (MZK) equation for the coupled drift acoustic wave in a non-uniform magnetized plasma. We highlight the differences between the MZK equation and its homogeneous counterpart. We also find the solution of the MZK equation using the tangent hyperbolic method. It is observed that the electron spectral index ${\it\kappa}$, positron concentration, and propagation angle ${\it\alpha}$ alter the structure of the ion acoustic drift solitary waves. The results obtained in this paper may be beneficial to understanding the propagation characteristics of electrostatic drift solitary structures in the interstellar medium and in laboratory experiments where electron–positron plasmas have recently been created by impinging ultra-intense laser pulses on a solid density target at the Lawrence Livermore National Laboratory (LLNL).