Nonlinear ion cyclotron and ion-acoustic waves have been studied in an electron–positron–ion plasma. Using Boltzmann distributions for the electrons and positrons and fluid equations for the ions, a set of nonlinear equations in the rest frame of the propagating wave is derived and numerically solved for the electric field. A scan of parameter space reveals a range of solutions for the parallel electric field, from sinusoidal to sawtooth to highly spiky waveforms. The results are compared with satellite observations.

Gas-filled capillary discharge waveguides are a commonly employed medium in laser–plasma interaction applications, such as the laser wakefield accelerator, because they can simultaneously guide high-power laser pulses while acting as the medium for acceleration. In this paper, the production of both straight and linearly tapered capillaries using a femtosecond laser micromachining technique is presented. A tapered capillary is shown to possess a smooth variation in diameter (from 305 μm to 183 μm) along its entire 40 mm length, which would lead to a longitudinal plasma density gradient, thereby dramatically improving the laser–plasma interaction efficiency in applications. Efficient guiding with up to 82% energy transmission of the fundamental Gaussian mode of a low intensity, 50 fs duration laser pulse is shown for both types of capillary waveguide.

The arbitrary amplitude Langmuir solitons are investigated in an unmagnetized, warm, relativistic plasma, consisting of electrons and positrons. Both the species are considered to have equal non-relativistic temperatures, but can have arbitrary relativistic drift speeds, and their dynamics are governed by fluid equations. Using the Sagdeev psuedo-potential approach, the effects of drift speed, Mach number, and thermal temperature on the amplitude and width of the Langmuir solitons are investigated. For the parameters considered, only rarefactive solitons are found. These solitons represent dip in electron density or electron holes in the configuration space. Existence domain of the Langmuir solitons is limited by the minimum and maximum Mach numbers for given parameters. An increase in the electron (positron) temperature leads to an increase in the Langmuir soliton amplitude and their half-widths. On the other hand, increasing the electron (positron) drift speeds results in decreasing soliton amplitudes and their half-widths. For some typical parameters corresponding to the pulsar magnetosphere, namely electron density ~106 cm−3 and electron thermal velocity of one-tenth of the velocity of light, the electric field of the Langmuir solitons can be of the order of (3–24)kV/m. The presence of such large amplitude electrostatic solitary structures may accelerate electrons and positrons and also produce fine structures of (1–5) microseconds in pulsar radio emissions.

Ionization-induced injection into a laser-driven wakefield is studied using 2½D OSIRIS simulations. A laser propagates into a gas mixture of 99.5% helium and 0.5% nitrogen with gas density of each rising linearly from 0 to a peak, after which these remain constant. Simulations show that the process can be controlled by varying the scale length of an up-ramp, the laser intensity, and the maximum plasma density. The injection process is controlled by the bubble radius decreasing as laser propagates up the density gradient and laser self-focusing in the flat-top region. A beam with a central energy of 350 MeV and an energy spread (FWHM) of 1.62% was obtained for an up-ramp length of 135 μm, a normalized vector potential of 2, and a density of 7 × 1018cm−3 (assuming a 0.8 μm wavelength laser).

The terahertz (THz) frequency radiation produced as a result of nonlinear interaction of high intense laser beam with low-density ripple in collisionless magnetoplasma has been studied under the paraxial ray approximation. The relativistic change of electron mass leads to self-focusing of laser beam when the initial power of laser beam is greater than its critical power. The self-focused laser beam couples with the pre-existing density ripple to produce a nonlinear current driving the THz radiation at different frequency. The applied magnetic field enhances the nonlinear coupling efficiency. Appropriate expressions for the beam width parameter of the laser beam and the electric vector of the THz wave have been evaluated. Theory and numerical simulations show that this THz source is capable of providing power of Giga watt level.

Basic features of obliquely propagating dust ion-acoustic (DIA) solitary waves, and their multidimensional instability in a magnetized dusty electronegative plasma (DENP) containing Boltzmann electrons, Boltzmann negative ions, adiabatic mobile positive ions, and negatively charged stationary dust have been theoretically investigated by reductive perturbation method and small-k perturbation expansion technique. The combined effects of ion adiabaticity, external magnetic field (obliqueness), and negatively charged dust, which are found to significantly modify the basic properties (speed, amplitude, width, and instability) of small but finite-amplitude DIA solitary waves, are explicitly examined. It is also found that the instability criterion and the growth rate of unstable perturbation are significantly modified by the external magnetic field, the propagation directions of both the nonlinear waves, and their perturbation modes. The implications of our results in space and laboratory dusty plasmas are briefly discussed.

In the present paper, quasilinear development of anisotropy-driven electromagnetic instabilities is computed on the basis of recently formulated empirical wave dispersion relation and compared against exact numerical calculation based upon transcendental plasma dispersion function and exact numerical roots. Upon comparison with the exact method it is demonstrated that the empirical model provides reasonable results. The present findings may be relevant to space physical application, as the present paper provides a useful short-cut research method for self-consistent analysis of temporal development of anisotropy-driven instabilities.

A pre-bunched relativistic electron beam (REB) counter-propagating to the surface wave in the vacuum region Compton backscatters the surface wave into a high-frequency coherent radiation. Plasma supports the surface wave that acquires a large wave number k0z around pump wave frequency $\omega _0 = {{\omega _p } {/ {\vphantom {{\omega _p } {\sqrt 2 }}} \kern-\nulldelimiterspace} {\sqrt 2 }}$, where ωp is the plasma frequency. The surface wave extends into the vacuum region and can be employed as a wiggler for the generation of sub-millimeter waves. The growth rate, efficiency, and gain were evaluated based on experimentally known parameters relevant to free electron laser (FEL). It was found that the growth rate, efficiency, and gain of the surface wave-pumped FEL increase with the modulation index Δ, which has the maximum value when approaching unity in addition to when the frequency and wave number of the pre-bunched beam are comparable to that of the radiation wave, i.e., ω01 ~ ω1 and k01 ~ k1. The growth rate of FEL instability scales as one-third power of beam density in the Compton regime.

This paper presents the effect of laser beam filamentation on the localization of electron plasma wave (EPW) and stimulated Raman scattering (SRS) in unmagnetized plasma when relativistic and ponderomotive nonlinearities are operative. The splitted profile of the laser beam is obtained due to uneven focusing of the off-axial rays. The semi-analytical solution of the nonlinearly coupled EPW equation in the presence of laser beam filaments has been found. It is observed that due to this nonlinear coupling between these two waves, localization of EPW takes place. Stimulated Raman scattering of this EPW is studied and back reflectivity has been calculated. Further, the localization of EPW affects the eigenfrequency and damping of plasma wave. The new enhanced damping of the plasma wave has been calculated and it is found that the SRS process gets suppressed due to the localization of plasma wave in laser beam filamentary structures.

The ion wake-field effects on the elastic electron–dust collisions are investigated in complex dusty plasmas. The eikonal method is employed to investigate the behaviors of the scattering phase shift and scattering cross section due to the variation of the strength of the wake-field. It is shown that the eikonal phase shift decreases with an increase of the Mach number and increases with an increase of the impact parameter. It is also shown that the eikonal phase shift decreases with increasing Debye length. The eikonal cross section for the elastic electron–dust collision is found to be increased due to the influence of the wake-field. In addition, it is found that the wake-field effect on the eikonal cross section is almost independent of the Debye length.

Complex plasmas are low-temperature plasmas containing micron-sized particles (microparticles) such as dust grains. These are present in astrophysical systems (comets, molecular clouds, et al.) and in technological applications (microchip production by plasma etching, deposition of solar cells, et al.). Complex plasmas are also of interest in basic science because these are often used as models for many other strongly coupled many-body systems in solid state, fluid, or plasma physics. Since gravity has a strong influence on the microparticle component, experiments under microgravity (parabolic flights, sounding rockets, International Space Station (ISS)) are performed. Interaction between microparticles depends on plasma parameters such as ion density or ion temperature. Also, the presence of microparticles may change the properties of background plasma. Therefore, the background plasma needs to be characterized to provide adequate interpretation of the microgravity experiments. For this purpose a dedicated high-speed diagnostic system has been set up.

In this paper, a homogeneous system of unmagnetized collisionless plasma consisting of a cold electron fluid, low-temperature ion obeying Boltzmann-type distribution and high-temperature ion obeying non-thermal distribution is considered. The perturbation method with two different forms of stretching will be considered to drive the KdV and modified KdV (mKdV) equations. The Agrawal's method is applied to formulate the time-fractional KdV and mKdV equations. A variational iteration method is used to solve these equations. The results show that the fractional order of the differential equations can be used to modify the shape of the solitary pulse instead of adding higher order dissipation terms to the equations. This study may be useful to construct the compressive and rarefactive electrostatic potential pulses associated with the broadband electrostatic noise type emissions.

The generation of 1–5 MeV protons from the interaction of a 3 ps TW CO2 laser pulse with a gas target with a peak density around the critical plasma density has been studied by 2D particle-in-cell simulations. The proton acceleration in the preformed plasma with a symmetric, linearly ramped density distribution occurs via formation of sheath of the hot electrons on the back surface of the target. The maximum energy of the hot electrons and, hence, net acceleration of protons is mainly defined by Forward Raman scattering instability in the underdense part of the plasma. Forward directed ion beams from a debris free gaseous target can find an application as a high-brightness ion source-injector to a conventional accelerator operating up to kHz pulse repetition frequency.

We investigate the Weibel instability in counter-propagating electron–ion plasmas with focus on the ion contribution, considering a realistic mass ratio. A generalized dispersion relation is derived from the relativistic theory by assuming an initially anisotropic temperature, which is represented by a waterbag distribution in momentum space, which shows an enhanced growth rate due to ion response. Two-dimensional particle-in-cell simulations support the theoretical analysis, showing a further amplification of magnetic field on ion time scale. The effect of an initial anisotropic temperature is investigated showing that the growth rate is monotonously decreased if the transverse spread is increased. Nevertheless, the presence of ions generates that the instability can develop for significantly higher electron temperatures. Suppression of oblique mode is also explored by introducing a parallel velocity spread.

A plasma chamber was constructed for the synthesis of ZnS nanoparticles in ionic liquid by glow discharge electrolysis method. Current and voltage (I-V) characteristics of the discharge at the metal–ionic liquid interface showed that the curve follows Ohm's law up to a particular voltage only so that the ZnS nanoparticle preparation was performed after the critical voltage. X-ray diffraction and energy dispersive spectral analysis showed that the samples contain ZnS nanoparticles and also found that tungsten from the metal electrode dissolved in the BMIM[BF4] ionic liquid under plasma and formed tungstic oxide by accepting atmospheric oxygen.

We have investigated some linear as well as nonlinear properties of ion-acoustic wave (IAW) propagation in a non-uniform two-electron-temperature magnetoplasma in the presence of ion-sheared flows. In the linear limit, new dispersion relation has been derived and analyzed in some interesting limiting cases. It is shown that ion-sheared flow can drive the IAW unstable under a certain limit.Whereas, in the nonlinear case, dipolar and vortex street type solutions can appear. It is observed that by choosing some typical parameters of Earth's auroral region, the scalelength of the nonlinear structures are significantly modified. The present investigation might be very useful to explain various types of nonlinear structure formation which has been observed in space environments where two-electron-temperature plasma exist.

Relativistic shocks are present in a number of objects where violent processes are accompanied by relativistic outflows of plasma. The magnetization parameter σ = B2/4πnmc2 of the ambient medium varies in wide range. Shocks with low σ are expected to substantially enhance the magnetic fields in the shock front. In non-relativistic shocks the magnetic compression is limited by nonlinear effects related to the deceleration of flow. Two-fluid analysis of perpendicular relativistic shocks shows that the nonlinearities are suppressed for σ≪1 and the magnetic field reaches nearly equipartition values when the magnetic energy density is of the order of the ion energy density, Beq2 ~ 4πnmic2γ. A large cross-shock potential eφ/mic2γ0 ~ B2/Beq2 develops across the electron–ion shock front. This potential is responsible for electron energization.

We present design considerations for the use of laser-plasma accelerators for mimicking space radiation and testing space-grade electronics. This novel application takes advantage of the inherent ability of laser-plasma accelerators to produce particle beams with exponential energy distribution, which is a characteristic shared with the hazardous relativistic electron flux present in the radiation belts of planets such as Earth, Saturn and Jupiter. Fundamental issues regarding laser-plasma interaction parameters, beam propagation, flux development, and experimental setup are discussed.

Excitation of the geodesic acoustic mode continuum by drift wave turbulence is studied using the wave kinetic approach. For a model profile of weak non-uniform ion temperature, the forms of growth rate and radial structure of geodesic acoustic modes are obtained analytically. The growth rate is analyzed for several conditions for present-day tokamaks and compared with that for uniform ion temperature, as well as that given by the coherent mode approach for non-uniform ion temperature.

A general theory for the existence of solitary structure at M = Mc has been discussed, where Mc is the lower bound of the Mach number M, i.e., solitary structures start to exist for M > Mc. Three important results have been proved to confirm the existence of solitary structure at M = Mc. If V(φ)(≡ V(M,φ)) denotes the Sagdeev potential with φ being the perturbed field or perturbed dependent variable associated with a specific problem, V(M, φ) is well defined as a real number for all M ∈ ℳ and φ ∈ Φ0, and V(M, 0) = V′(M, 0) = V″(Mc, 0) = 0, V‴(Mc, 0) < 0 (V‴(Mc, 0) > 0), ∂ V/∂ M < 0 for all M (∈ ℳ) > 0 and φ (∈ Φ0) > 0 (φ (∈ Φ0) < 0), where ‘′ ≡ ∂/∂φ’, the main analytical results for the existence of solitary wave or double layer solution of the energy integral at M = Mc are as follows. Result 1: If there exists at least one value M0 of M such that the system supports positive (negative) potential solitary waves for all Mc < M < M0, then there exists either a positive (negative) potential solitary wave or a positive (negative) potential double layer at M = Mc. Result 2: If the system supports only negative (positive) potential solitary waves for M > Mc, then there does not exist positive (negative) potential solitary wave at M = Mc. Result 3: It is not possible to have coexistence of both positive and negative potential solitary structures at M = Mc. Apart from the conditions of Result 1, the double layer solution at M = Mc is possible only when there exists a double layer solution in any right neighborhood of Mc. Finally, these analytical results have been applied to a specific problem on dust acoustic (DA) waves in non-thermal plasma in search of new results.