Nonthermal Ions Research Articles

Oblique Propagation of Low-Frequency Solitary Waves in a Magnetized Polarized Complex Plasma With Adiabatically Trapped Nonthermal Ions

The oblique propagation of low-frequency solitary waves is considered in a polarized magnetized complex plasma with adiabatically trapped nonthermalions. A Cairns–Gurevich distribution is adopted, and the polarization force associated with our plasma model is applied. In addition, the appropriate modified Korteweg–de Vries (mK-dV) equation, in which the Cairns–Gurevich polarization force and external magnetic field are taken into account, is established. Our numerical investigation applied to space dusty plasma reveals that the amplitude and the width of the dust acoustic (DA) solitary structure are significantly modified by the effects of the magnitude of the external static magnetic field <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\omega _{c}$ </tex-math></inline-formula> as well as the obliquity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$l_{z}$ </tex-math></inline-formula> and polarization force. In particular, we have found that for given values of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$l_{z}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\omega _{c}$ </tex-math></inline-formula> , the DA soliton profile becomes more profound due to the presence of Cairns–Gurevich polarization force. For the sake of completeness, we have also analyzed both the effects of Cairns–Gurevich polarization force and the external magnetic field on DA soliton energy. In particular, we have shown that the energy quantities are shifted, for any value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$l_{z}$ </tex-math></inline-formula> , toward large values, in the presence of polarization force.

Microphysics of Relativistic Collisionless Electron-ion-positron Shocks

We perform particle-in-cell simulations to elucidate the microphysics of relativistic weakly magnetized shocks loaded with electron-positron pairs. Various external magnetizations σ ≲ 10−4 and pair-loading factors Z ± ≲ 10 are studied, where Z ± is the number of loaded electrons and positrons per ion. We find the following: (1) The shock becomes mediated by the ion Larmor gyration in the mean field when σ exceeds a critical value σ L that decreases with Z ±. At σ ≲ σ L the shock is mediated by particle scattering in the self-generated microturbulent fields, the strength and scale of which decrease with Z ±, leading to lower σ L. (2) The energy fraction carried by the post-shock pairs is robustly in the range between 20% and 50% of the upstream ion energy. The mean energy per post-shock electron scales as . (3) Pair loading suppresses nonthermal ion acceleration at magnetizations as low as σ ≈ 5 × 10−6. The ions then become essentially thermal with mean energy , while electrons form a nonthermal tail, extending from to . When σ = 0, particle acceleration is enhanced by the formation of intense magnetic cavities that populate the precursor during the late stages of shock evolution. Here, the maximum energy of the nonthermal ions and electrons keeps growing over the duration of the simulation. Alongside the simulations, we develop theoretical estimates consistent with the numerical results. Our findings have important implications for models of early gamma-ray burst afterglows.

Observation of non-thermal metastable ion velocity distributions in a miniaturized multi-dipole confined plasma device

Hot cathode discharges are common plasma sources for fundamental plasma physics studies and other applications due to their capability to produce quiescent plasma. This work presents experimental observations of presheath-associated non-thermal metastable ion velocity distributions in a miniaturized multi-dipole confined plasma device measured by laser-induced fluorescence. The intensity of this non-Maxwellian component is related to the collisions of these metastable ions with background particles. Additionally, the flow velocity of this component is lower than the Bohm velocity; thus, its energy is lower than the presheath potential drop kTe/2. This implies that these non-thermal metastable ion velocity distributions are formed via presheath acceleration and are associated with the source asymmetries of the miniaturized device. The strength decreases as the neutral pressure increases once the neutral pressure is adjusted, suggesting that the presheath length is the critical condition that determines whether these components can be observed.

Modulational Instability Analysis of Four-Component Dusty Plasma System

Dust in plasma is a major hindrance for many scientific activities that occur in space, fusion, and so on. One of the crucial properties that makes sense for such hindrance is its nonlinearity. Existence of solitons proves the condition of nonlinearity and by enabling the significance of such solitons, nonlinearity can be minimized to an extent. Our own selves conceptually probed the four-component dusty plasma system and the four components are positive and negative dust components, two components of electrons and non-thermal ions modeled by Boltzmann distributions. The nonlinear reductive perturbation technique is employed and we derived the nonlinear Schrödinger equation (NLSE), which governs the nonlinear dynamics of the plasmic system. Furthermore, we invoke the modulational instability (MI) analysis to inspect the stability of plasmic solitons and the instability/stability regions of dust ion acoustic (DIA) waves are highly explored.

Study of Scattering of Non-Linear Wave in Dusty Plasma with Non-Thermal Ions

Research on Scattering of Non-Linear Wave has a wide applications and support - for Spectroscopic behavior of atomic modeling in terms of Plasma models. As the precision and scope of spectroscopic models has increased, the atomic modeling also has had to evolve. With a focus now on ITER and the dusty plasma with non-thermal ions. The characteristics of Dust- Acoustic Solitary Waves (DASWs) and Double Layers (DLs) are studied. Ions are treated as non-thermal and variable dust-charge is considered. The study in further extended to investigate the possibility of DLs. Only compressive DLs are permissible.

Shock waves in a strongly coupled inhomogeneous dusty plasma

Nonlinear theory for certain dust acoustic waves has been developed for a strongly coupled inhomogeneous collisionless dusty plasma containing dust particles of different sizes. The generalized hydrodynamic set of partial differential equations is considered to describe the fluid model of the present nonlinear system. A reductive perturbation technique is employed on this nonlinear set of equations to derive a variable coefficient Korteweg-deVries (KdV)–Burgers equation with a forcing term. The generalized expansion method is performed to obtain an analytic expression for the solution. This analytic solution describes the monotonic kink-type shock waves, due to the dominant nature of the dissipation term over the dispersion term. In addition to the effects of inhomogeneity and grain size distribution, the effects of nonthermal ions, dust–dust correlation and ion temperature on the wave propagation are investigated. Also, a steady-state monotonic shock solution of the KdV-Burgers equation is obtained numerically. The obtained results are discussed in the context of some dusty plasmas, previously reported experimentally or theoretically.

Propagation characteristics of (2 + 1) dimensional dust acoustic solitary waves in hot dusty plasma

The propagation characteristics of (2 + 1) dimensional nonlinear dust acoustic solitary wave in an unmagnetized hot dusty plasma composed of dust particles, electrons and nonthermal ions are studied in the paper. Firstly, the Kadomtsev-Petviashvili (KP) equation, which is used to describe the (2 + 1) dimensional nonlinear dust acoustic solitary wave, is derived by the reduced perturbation method, and the phase diagram and the Sagdeev potential equation of the system are obtained by using the traveling wave solution method. Then, the effects of different parameters in the hot dusty plasma system on the nonlinear coefficient, dispersion coefficient of the KP equation, system phase diagrams, Sagdeev potential function and the solitary wave solution in isothermal and adiabatic states are discussed by using numerical simulation and analysis method of mathematical software. Finally, the results show that the mass of dust particles, temperature, number density and distribution state of electrons and nonthermal ions have important effects on the amplitude, width and waveform of the nonlinear dust acoustic solitary wave under isothermal and adiabatic conditions.

Progressive Thermalization Fusion Reactor Able to Produce Nuclear Fusions at Higher Mechanical Gain

In the standard fusion reactors, mainly tokamaks, the mechanical gain obtained is below 1. On the other hand, there are colliding beam fusion reactors, for which, the not neutral plasma and the space charge limit the number of fusions to a very small number. Consequently, the mechanical gain is extremely low. The proposed reactor is also a colliding beam fusion reactor, configured in Stellarator, using directed beams. D+/T+ ions are injected in opposition, with electrons, at high speeds, so as to form a neutral beam. All these particles turn in a magnetic loop in form of figure of “0” (“racetrack”). The plasma is initially non-thermal but, as expected, rapidly becomes thermal, so all states between non-thermal and thermal exist in this reactor. The main advantage of this reactor is that this plasma after having been brought up near to the optimum conditions for fusion (around 68 keV), is then maintained in this state, thanks to low energy non-thermal ions (≤15 keV). So the energetic cost is low and the mechanical gain (Q) is high (>>1). The goal of this article is to study a different type of fusion reactor, its advantages (no net plasma current inside this reactor, so no disruptive instabilities and consequently a continuous working, a relatively simple way to control the reactor thanks to the particles injectors), and its drawbacks, using a simulator tool. The finding results are valuable for possible future fusion reactors able to generate massive energy in a cleaner and safer way than fission reactors.

The Electrodynamic Mechanism of Collisionless Multicomponent Plasma Expansion in Vacuum Discharges: From Estimates to Kinetic Theory

This paper is devoted to the study of collisionless multicomponent plasma expansion in vacuum discharges. Based on the fundamental principles of physical kinetics formulated for vacuum discharge plasma, an answer is given to the following question: What is the main mechanism of cathode plasma transport from cathode to anode, which ensures non-thermal metallic positive ion movement? Theoretical modeling is provided based on the Vlasov–Poisson system of equations for a current flow in a planar vacuum discharge gap. It was shown that the non-thermal plasma expansion is of a purely electrodynamic nature, caused by the formation of a “potential hump” in the interelectrode space and its subsequent movement under certain conditions consistent with plasma electrodynamic transportation. The presented results reveal two cases of the described phenomenon: (1) the dynamics of single-component cathode plasma and (2) multicomponent plasma (consisting of multiple charged ions) expansion.

Efficient Nonthermal Ion and Electron Acceleration Enabled by the Flux-Rope Kink Instability in 3D Nonrelativistic Magnetic Reconnection.

The relaxation of field-line tension during magnetic reconnection gives rise to a universal Fermi acceleration process involving the curvature drift of particles. However, the efficiency of this mechanism is limited by the trapping of energetic particles within flux ropes. Using 3D fully kinetic simulations, we demonstrate that the flux-rope kink instability leads to strong field-line chaos in weak-guide-field regimes where the Fermi mechanism is most efficient, thus allowing particles to transport out of flux ropes and undergo further acceleration. As a consequence, both ions and electrons develop clear power-law energy spectra that contain a significant fraction of the released energy. The low-energy bounds are determined by the injection physics, while the high-energy cutoffs are limited only by the system size. These results have strong relevance to observations of nonthermal particle acceleration in space and astrophysics.

Inward and outward dust acoustic cylindrical and spherical waves interaction in four-component dusty plasma with nonthermal ions

Abstract A theoretical investigation by an all-inclusive adaptation of the PLK strategy is carried out in order to study the inward and outward interaction between two cylindrical and spherical dust acoustic solitary waves (DASWs) in an unmagnetized dusty plasma consisting of nonthermal distributed ions, negatively and positively charged dust grains along with electrons featuring Boltzmann’s distribution. The interactions and collisions between two cylindrical and spherical geometries at different time scales are studied. Also the combined effects of the nonthermality of ions, ion to electron temperature ratio as well as mass ratio of positive to negative dust grains have been studied in detail on the phase shifts raised due to collision. It has been seen that the properties of the cooperation of DASWs in cylindrical and spherical shaped are distinct.

Low‐frequency variable charge solitary waves in a collisionless dusty plasma with a Cairns‐Gurevich ion velocity distribution

AbstractIn this paper, the problem of large amplitude dust acoustic (DA) solitons has been addressed in a charge varying dusty plasma with ions following a Cairns‐Gurevich distribution. Based on the orbit motion limited approach, the correct Cairns‐Gurevich ion charging current is presented for the first time. The expression relating the variable dust charge to the plasma potential is given in terms of the Lambert function and we take advantage of this transcendental function to, carefully, analyse DA solitons in a charge varying dusty plasma with trapped nonthermal ions. Our results show that the spatial patterns of the variable charge solitary wave are significantly changed due to the presence of ion population modelled by the Cairns‐Gurevich distribution. An addition of a small concentration of trapped nonthermal ions makes the solitary structure less spiky, grows the net negative charge residing on the dust grain surface, and contributes to the electron depletion. Finally, our investigation is extended to highlight the effect of the grain dust charge variation. We have shown that under certain conditions, the impact of dust charge fluctuation may furnish an alternate physical mechanism rasing anomalous dissipation, which becomes more strong and may predominate over the dispersion as the nonthermal character of ions following the Cairns‐Gurevich distribution increases.

Dust-acoustic solitary and cnoidal waves in a dense magnetized dusty plasma with temperature degenerate trapped electrons and nonthermal ions

A rigorous theoretical study has been made on obliquely propagating dust-acoustic solitary waves (OPDASWs) and cnoidal waves in a dense degenerate dusty plasma medium in the presence of temperature degenerate trapped electrons and κ−nonthermal ion population. A reductive perturbation technique has been adopted to obtain the Zakharov-Kuznetsov (ZK) equation and the modified ZK (mZK) equation. The solitary wave solutions of ZK and mZK equations are obtained to analyse the characteristics of solitary waves in such a plasma. The Jacobi (cn) elliptic periodic wave solution for mZK is also derived to analyse the nature of dust acoustic travelling wave. The different plasma parameters (e.g., electron-to-dust number density via δ, ions nonthermality via κ, temperature effect of degenerate trapped electrons via T, etc.) are seen to have significant inluence on the propagation nature of OPDASWs. The applications of results may be useful to explain/understand the nature of solitary waves in different ultra-dense astrophysical environments (such as neutron stars, white dwarfs etc. [, ]) and also in experiments involve the interaction of laser and solid density plasma and inertial confinement fusion, [, ] in which the relativistic effects play major role.

Adapted instabilities excited in spherical magnetized viscoelastic astroclouds with extreme dust-fugacity moderations

We investigate the dynamics of the dust acoustic wave (DAW, low-fugacity) and the dust Coulomb wave (DCW, high-fugacity) in self-gravitating magnetized viscoelastic spherical dusty astroclouds. It consists of the inertial dust grains with variable charge alongside the nonthermal electrons and ions in a generalized hydrodynamic framework. A spherical wave analysis yields a unique generalized quadratic dispersion relation. The fluctuations are free from the viscoelasticity effects in the weakly coupled limit (WCL) against the strongly coupled limit (SCL). The electron concentration, dust charge, and magnetic field act as stabilizing and accelerating agencies. The ion density and nonthermality parameters show destabilizing and decelerating effects. The cloud size shows a unique stabilizing feature in the ultralow-frequency domain. Both the DAW and DCW are dispersive in the short-wavelength (acoustic) regime and nondispersive in the long-wavelength (gravitational) regime. The distinctive WCL–SCL scenarios are explicitly compared. The results show correlative consistencies in real astronomic circumstances sketchily. The dust acoustic wave (DAW) and the dust Coulomb wave (DCW) in self-gravitating magnetized viscoelastic spherical dusty astroclouds with extreme dust-fugacity moderations are explored. The spatiospectral profiles of (a) $$\Omega_{r}$$ and (b) $$\Omega_{i}$$ with $$K$$ and $$\xi$$ in the SCL (upper row) and in the WCL (lower row) of the HFR in the $$\kappa$$ -case are numerically portrayed.

Full particle-in-cell simulation of the formation and structure of a collisional plasma shock wave.

The formation and structure of a collisional shock wave in a fully ionized plasma is studied via full particle-in-cell simulations, which allows the complex momentum and energy transfer processes between different charged particles to be treated self-consistently. The kinetic energy of the plasma flow drifting towards a reflecting piston is found to be rapidly converted into thermal motion under the cooperative effects of ion-ion collisions, ion-electron collisions, and electric field charged-particle interactions. The subsequent shock evolution is influenced by the "precursor" ion beam before a quasisteady state is reached. The shock wave structure is then analyzed from a two-fluid transport viewpoint, which is found to be affected by "flux-limiting" electron transport, the nonthermal ions, and the charge separation electric field.

Ion Acceleration in Driven Magnetic Reconnection during High-energy–Density Plasma Interaction

Abstract Strongly driven magnetic reconnection occurs in astrophysical events and also in laboratory experiments with laser-produced plasma. We have performed 2.5D particle-in-cell simulations of collisions of two high-energy–density plasmas resulting in strongly driven magnetic reconnection that demonstrates significant non-thermal ion acceleration. Such acceleration is significant only when the plasma beta is sufficiently low that the Alfvén speed at the reconnection inflow exceeds the thermal speed. Under these conditions, the most energetic ions are primarily accelerated by the Hall electric field in the reconnection outflow, especially at the trailing edge of an emerging plasmoid in the outflow. Laboratory experiments in the near future should be able to confirm these predictions and their applicability to astrophysical situations.

Low-frequency solitary wave propagations in complex plasmas: the effect of trapped non-thermal polarization force

ABSTRACT The effect of trapped non-thermal polarization force on low-frequency solitary waves (dust acoustic solitons) is addressed in a collisionless complex plasma. For this purpose, we have firstly redefined the three-dimensional Cairns–Gurevich distribution that describes, simultaneously, the evolution of the energetic ions and those trapped in the plasma potential well, and derived the associated both density and polarization force expressions. The polarization force effects are remarkably modified due to the presence of the trapped non-thermal ions. In particular, we have found that the polarization force magnitude decreases with the increase of ion non-thermality character. Next, the modifications arising in dust-acoustic (DA) solitons and its energy due to the presence of these trapped non-thermal density and polarization force are analyzed. In particular, we have found that the presence of the polarization force leads to an increase in the amplitude and width of DA solitary wave can be propagated in different complex plasma media. Finally, a complementary study on the polarization force effects on the DA energy, associated with both space and experimental dusty plasmas, is also carried out. Our numerical results have shown that more is strong the polarization force more is higher the energy transported by DA solitons.

Instability of Dust–Acoustic Waves in Plasmas with Two-Temperature Nonthermal Ions

Theoretical and numerical investigations are carried out for the instability of the dust–acoustic waves (DAWs) under the transverse perturbation in a magnetized dusty plasma with two-temperature nonthermal ions. By the reductive perturbation technique, the Zakharov–Kuznetsov (ZK) equation and modified ZK equation of the DAWs are derived. Under the higher-order transverse perturbations, the instability growth rate of the soliton solutions of the ZK equations is studied. It is found that the most unstable wave mode exists in system. It is also noted that solitary waves are unstable when the ratio of the perturbation wave length to solitary wave width in the experimental coordinate is larger than a certain critical value.

Dust-acoustic solitary waves in a self-gravitating warm opposite polarity dusty plasma

A theoretical investigation is made to study the propagation of dust-acoustic solitary waves in a general and realistic self-gravitating dusty plasma system containing positively as well as negatively charged warm dust species and nonthermally distributed ion species. The standard reductive perturbation method is employed to derive the Korteweg–de Vries equation which admits the solitary wave solution. The parametric regimes for the existence of dust-acoustic solitary waves associated with electrostatic and self-gravitational potentials are obtained. It is shown that the population of nonthermal ion species significantly modifies the basic features of the dust-acoustic solitary waves. The significant effects of ratios of mass, temperature, and number density of positively charged dust species to those of negatively charged one on the basic properties (namely, phase speed, polarity, amplitude, and width) of the dust-acoustic solitary waves are also identified. A brief comparison between electrostatic and self-gravitational solitary potential structures is also made. The implications of our results to different space and laboratory dusty plasma environments, where opposite polarity dust grains are observed, are briefly discussed.

Breather Structures and Peregrine Solitons in a Polarized Space Dusty Plasma

In this theoretical investigation, we have examined the combined effects of nonthermally revamped polarization force on modulational instability MI of dust acoustic waves DAWs and evolution of different kinds of dust acoustic (DA) breathers in a dusty plasma consisting of negatively charged dust as fluid, Maxwellian electrons, and ions obeying Cairns’ nonthermal distribution. The nonthermality of ions has considerably altered the strength of polarization force. By employing the multiple-scale perturbation technique, the nonlinear Schrödinger equation NLSE is derived to study modulational MI instability of dust acoustic waves DAWs. It is noticed that influence of the polarization force makes the wave number domain narrow where MI sets in. The rational solutions of nonlinear Schrödinger equation illustrate the evolution of DA breathers, namely, Akhmediev breather, Kuznetsov–Ma breather, and Peregrine solitons (rogue waves). Further, the formation of super rogue waves due to nonlinear superposition of DA triplets rogue waves is also discussed. It is analyzed that combined effects of variation in the polarization force and nonthermality of ions have a comprehensive influence on the evolution of different kinds of DA breathers. It is remarked that outcome of present theoretical investigation may provide physical insight into understanding the role of nonlinear phenomena for the generation of various types of DA breathers in experiments and different regions of space (e.g., the planetary spoke and cometary tails).