Plasma Frequency Research Articles

Juno Observations of Langmuir Waves in Association with Interplanetary Shocks from ~1.3 to ~5.4 au

Abstract Langmuir waves are often observed upstream of planetary bow shocks and interplanetary (IP) shocks. Waveform capture (WFC) measurements, obtained during Juno’s cruise phase, reveal the occurrence of Langmuir waves, as well as other wave modes, in association with IP shocks and IP coronal mass ejections (ICMEs) at distances from ∼1.3 to ∼5.4 au. This is a unique database of ICME/IP shock events with WFCs in the equatorial plane in these radial distances. We identified 12 events when WFCs were obtained within 36 hr upstream of the IP shock/ICME event (10 within less than 10 hr). Langmuir waves were observed at 9, a significantly higher occurrence than has previously been reported using spectral observations from other spacecraft. The larger rate is likely due to the bursty nature of Langmuir waves in combination with the higher time resolution of WFC data compared to spectral data. Observed peak amplitudes of ∼16 mV m−1 (peak to peak) are comparable to those observed upstream of outer planetary bow shocks. The highest peak amplitudes occurred in the strongest shocks (largest magnetic compression) and when waveforms were obtained closest to the shock. Langmuir waves were observed as much as 8 hr upstream. The WFCs provide electron density on rapid time scales, including an increase from ∼0.05 to 0.25 cm−3 in ∼0.01 s across an IP shock ramp. Although electron measurements were not obtained, these observations provide evidence for the energization of electrons at the shock or ICME front and, in some events, for propagation over large distances while maintaining the features in the distributions necessary to destabilize Langmuir waves.

Fermi-liquid behavior of nonaltermagnetic RuO2

The presence of magnetism in potentially altermagnetic RuO2 has been a subject of intense debate. Using broadband infrared spectroscopy combined with density-functional band-structure calculations, we show that the optical conductivity of RuO2, the bulk probe of its electronic structure, is best described by a nonmagnetic model. The sharp Pauli edge demonstrates the presence of a Dirac nodal line lying 45 meV below the Fermi level. An excellent match between the experimental and plasma frequencies underpins the weakness of electronic correlations. The intraband part of the optical conductivity indicates Fermi-liquid behavior with two distinct scattering rates below 150 K. Fermi-liquid theory also accounts for the temperature-dependent magnetic susceptibility of RuO2 and allows a consistent description of this material as a paramagnetic metal. Published by the American Physical Society 2025

Simulation of ion cyclotron range of frequencies heating in the proton–boron plasma of the spherical tokamak

Abstract Ion cyclotron range of frequencies (ICRF) heating is crucial in magnetic confinement fusion devices that utilize proton–boron11 (p11B) as an advanced fuel, as it requires higher ion temperatures for their reactions. This work investigates the ICRF heating characteristics of hydrogen (H) ions at the second harmonic frequency and 11B ions at the fundamental frequency in a p11B plasma within a spherical tokamak. It is found that H ions second harmonic is better than 11B ions fundamental for ion power absorption. We simulate the ICRF heating effects of the 11B fraction in plasma and the wave vector parallel to the magnetic field ( k ‖ ) of the antenna using full-wave codes and the kinetic dispersion relation solver. In second harmonic heating of H ions, the power deposition primarily occurs on the H ions themselves, and, the total power absorption will exceed 50%, up to 58%, when X[11B] > 6%. Heating the electrons is easier in the fundamental frequency heating of 11B ions scenario.

Nano carbon powder‐multiwalled carbon nanotubes/poly(vinylidene fluoride) percolating composites with low‐percolation binary functional phases and negative permittivity

AbstractPolymer percolating composites with negative permittivity via the construction of percolating structures are of great interest in electromagnetism. In this study, nano carbon powder‐multiwalled carbon nanotubes/poly(vinylidene fluoride) (CP‐MWCNTs/PVDF) composites comprising binary functional phases CP‐MWCNTs were fabricated using hot‐pressing method. The composites achieved both low percolation threshold and tunable negative permittivity properties across the entire frequency range of testing. Percolation phenomenon was observed as functional phases content reaching 5 wt%, which was reflected as the establishment of percolation network and the occurrence of electrical percolation, resulting in a shift toward metal‐like conduction mechanism. Additionally, the notably low percolation threshold can be ascribed to the synergistic effect between the binary functional phases. The plasma oscillation of free electrons within conductive percolation network plays a crucial role in achieving negative permittivity, a phenomenon that can be elucidated using the Drude model from the free electron theory. Furthermore, analyses of the impedance and equivalent circuit illuminate the connection between percolation phenomenon and dielectric behavior. These findings further reveal the influence of functional phases' morphology and composition on percolation behavior and negative permittivity properties, while expanding the application of polymer‐based percolating composites in electromagnetic devices.Highlights Tunable negative permittivity related to plasma oscillation is achieved. Binary functional phases exhibit a low percolation threshold. Synergistic effect of functional phases leads to low percolation threshold.

All-mirror wavefront division interferometer for Fourier transform spectrometry across multiple spectral ranges.

We report on the design of an all-mirror wavefront-division interferometer capable of spectroscopic studies across multiple spectral ranges-from the plasma frequencies of metals to terahertz wavelengths and beyond. The proposed method leverages the properties of laser sources with high spatial coherence. A theoretical framework for the interferometer scheme is presented, along with an analytical solution for determining the far-field interference pattern, which is validated through both optical propagation simulations and experimental results. The practical implementation of the spectrometer, using cost-effective off-the-shelf components (knife-edge prisms for separation and recombination), is demonstrated. The system features ultra-broad optical bandwidth, high throughput, simple architecture, dispersion-free operation, and variable arm split ratio. These unique attributes make our approach a prospective alternative to standard Fourier transform spectrometer schemes, specifically tailored to laser-based scenarios. Further, the employed design inherently enables the measurement of the sample's dispersion. In the experimental section, we demonstrate the feasibility of spectroscopic measurements by coupling the system with a supercontinuum source with more than an octave-spanning range (1.5µm - 4.4µm). As a proof-of-concept, an experimental demonstration is provided for various applied spectroscopic studies: transmission measurements of polymers (polypropylene) and gas (methane), as well as reflectance measurements of dried pharmaceuticals (insulin products on a metal surface).

Benchmark between N-body, PIC, and semi-Lagrangian simulations of Landau-damped Langmuir wave

This work presents a benchmark study comparing three distinct numerical methods—Particle-In-Cell (PIC), semi-Lagrangian, and N-body simulations—for analyzing the damping of Langmuir waves in a one-dimensional Vlasov–Poisson plasma system. Each approach has unique advantages in terms of accuracy, resolution, and computational cost. The comparison aims to discriminate between numerical artifacts and physical phenomena, identifying the contribution of finite particle numbers and boundary conditions in both linear and nonlinear regimes. The study demonstrates strong agreement between the PIC and semi-Lagrangian methods in both regimes. N-body simulations, while requiring a specific method to overcome statistical noise, agree in the limit of many bodies (>500). Crucial subtleties regarding initial and boundary conditions are discussed throughout.

Parametric representation, asymptotic and bifurcation analyses of the electronic plasma oscillations

Parametric representation, asymptotic and bifurcation analyses of the electronic plasma oscillations

Synergizing microfluidics and plasmonics: advances, applications, and future directions.

In the past decade, interest in nanoplasmonic structures has experienced significant growth, owing to rapid advancements in materials science and the evolution of novel nanofabrication techniques. The activities in the area are not only leading to remarkable progress in specific applications in photonics, but also permeating to and synergizing with other fields. This review delves into the symbiosis between nanoplasmonics and microfluidics, elucidating fundamental principles on nanophotonics centered on surface plasmon-polaritons, and key achievements arising from the intricate interplay between light and fluids at small scales. This review underscores the unparalleled capabilities of subwavelength plasmonic structures to manipulate light beyond the diffraction limit, concurrently serving as fluidic entities or synergistically combining with micro- and nanofluidic structures. Noteworthy phenomena, techniques and applications arising from this synergy are explored, including the manipulation of fluids at nanoscopic dimensions, the trapping of individual nanoscopic entities like molecules or nanoparticles, and the harnessing of light within a fluidic environment. Additionally, it discusses light-driven fabrication methodologies for microfluidic platforms and, contrariwise, the use of microfluidics in the fabrication of plasmonic nanostructures. Pondering future prospects, this review offers insights into potential future developments, particularly focusing on the integration of two-dimensional materials endowed with exceptional optical, structural and electrical properties, such as goldene and borophene, which enable higher carrier densities and higher plasmonic frequencies. Such advancements could catalyze innovations in diverse applications, including energy harvesting, advanced photothermal cancer therapies, and catalytic processes for hydrogen generation and CO2 conversion.

Structural and linear/nonlinear optical characteristics of flexible polypyrrole/CuO polymeric composite films

The composite (PPy/CuO) films are created using the solution casting solution method by mixing the polymer polypyrrole (PPy) with copper oxide nanoparticles (CuONPs) at different concentrations of CuO (4%, 6% and 8%). The XRD confirms the effective fabrication of the composite (PPy/CuO). The impact of CuO on the optical and structural characteristics was studied. The addition of CuO enhances the refractive indices ([Formula: see text] of PPy from 1.42 for pure PPy to 1.55 for PPy with 4% CuO, and further to 1.69 for PPy with 8% CuO. The dispersion energy of pure polypyrrole (PPy) is 4.55[Formula: see text]eV, which increased to 5.31[Formula: see text]eV when doped with 4% CuO. Furthermore, the increasing of CuO concentration to 6% and 8% resulted in higher dispersion energies, respectively, of 5.87 and 6.14[Formula: see text]eV. The oscillation energy [Formula: see text] decreased from 4.43[Formula: see text]eV for PPy to 3.76, 3.41 and 3.25[Formula: see text]eV for PPy/4%CuO, PPy/6%CuO and PPy/8%CuO, correspondingly. The introduction of CuO into the PPy polymer results in modifications to its optical characteristics. Additionally, there was an observed rise in the plasma frequency from [Formula: see text][Formula: see text][Formula: see text] for PPy to [Formula: see text][Formula: see text][Formula: see text] for PPy/8%CuO. The findings of this study offer empirical support for the possible use of PPy/CuO films in optical devices.

Real-time electron density measurement technique using a microwave resonant probe for low-pressure plasmas

Abstract This paper presents a technique to perform a time-resolved electron density measurement in a plasma using a microwave resonant probe named curling probe and a Voltage Controlled Oscillator (VCO) fast-swept circuit. The technique is an interesting alternative to the Vector Network Analyzer (VNA) used in on-point mode on repetitive triggered discharges as it also works for non-repeatable events or in cases where trigger signals are unavailable. First, the temporal resolution of the presented setup is assessed to be 5 μs with an uncertainty on the electron density of 5x107 cm-3. Second, the accuracy of the diagnostic is successfully demonstrated by measuring similar electron density for different measurement rates and by measuring forced plasma oscillations at 25 kHz in a magnetic nozzle thruster. Third, the ability of the diagnostic to perform real-time measurements is demonstrated by capturing the transient dynamic of the electron density during the switch-off of the thruster, with a fast plasma density variation of the order of 6x107 cm-3/μs being measured during the first tens of microseconds after plasma extinction.

Resonant Conversion of Wave Dark Matter in the Ionosphere

We consider resonant wavelike dark matter conversion into low-frequency radio waves in the Earth’s ionosphere. Resonant conversion occurs when the dark matter mass and the plasma frequency coincide, defining a range mDM∼10−9–10−8 eV where this approach is best suited. Owing to the nonrelativistic nature of dark matter and the typical variational scale of the Earth’s ionosphere, the standard linearized approach to computing dark matter conversion is not suitable. We therefore solve a second-order boundary-value problem, effectively framing the ionosphere as a driven cavity filled with a positionally varying plasma. An electrically small dipole antenna targeting the generated radio waves can be orders of magnitude more sensitive to dark photon and axionlike particle dark matter in the relevant mass range. This Letter opens up a promising way of testing hitherto unexplored parameter space that could be further improved with a dedicated instrument. Published by the American Physical Society 2024

The fractional soliton solutions of the dynamical system of equations for ion sound and Langmuir waves: a comparative analysis.

In light of the ponderomotive force, this article focuses on establishing the exact wave structures of the ion sound system. It is the result of non-linear force and affects a charged particle oscillating in an inhomogeneous electromagnetic field. By using the Riemann-Liouville operator, -operator, and Atangana-Baleanu fractional analysis, the examined equation-which consists of the normalized electric field of the Langmuir oscillation and normalized density perturbation-is thoroughly examined. The solutions can be obtained with the help of a relatively new integration tool, the new extended direct algebraic method. We extract various wave structures in bright, dark, combo, ark, bright, and singular soliton solutions, among other forms, from soliton solutions. This method is simple and quick, and it can be used with more non-linear models or systems. Using the Mathematica software package, a graphically comparative analysis of some solutions is also presented here, taking appropriate parametric values into consideration.

Shadow and gravitational weak lensing around a quantum-corrected black hole surrounded by a plasma

Abstract In this paper, we delve into the optical properties of a quantum-corrected black hole (BH) in loop quantum gravity, surrounded by a plasma medium. We first determine the photon and shadow radii resulting from quantum corrections and the plasma medium in the environment surrounding a quantum-corrected BH. We find that the photon sphere and the BH shadow radii decrease due to the quantum correction parameter $\alpha$ acting as a repulsive gravitational charge. We further delve into the gravitational weak lensing by applying the general formalism used to model the deflection angle of the light traveling around the quantum-corrected BH placed in the plasma medium. We show, in conjunction with the fact that the combined effects of the quantum correction and non-uniform plasma frequency parameter can decrease the deflection angle, that the light traveling through the uniform plasma can be strongly deflected compared to the non-uniform plasma environment surrounding the quantum-corrected BH. Finally, we consider the magnification of the lensed image brightness under the effect of the quantum correction parameter $\alpha$, together with the uniform and non-uniform plasma effects.

First-principles study of electron dynamics of MoS2 under femtosecond laser irradiation from deep ultraviolet to near-infrared wavelengths.

Time-dependent density functional theory was employed to investigate the electron dynamics of MoS2 following femtosecond pulse irradiation. The study concerned the effects of laser wavelength, intensities, and polarization and elucidated the ionization mechanisms across the intensity range of 1010-1014 W/cm2. As laser intensity increases, MoS2 irradiated with an infrared (IR) laser (800nm) deviates from single-photon absorption at lower intensities compared to that subjected to an ultraviolet (UV) laser (266nm), and nonlinear effects in the current arise at lower intensities for the 800nm laser. At a wavelength of 266nm, MoS2 irradiated with an a-axis polarized laser deposited more energy and generated more electron-hole pairs compared to c-axis polarization. Rate equations were used to estimate the total number of excited electrons in MoS2 and the corresponding plasma frequency. Simulation results indicate that the damage threshold of the UV laser is higher than that of the IR laser, which contradicts the experimental results. This outcome suggests that the mechanism of material damage induced by the UV femtosecond laser near the damage threshold is independent of optical breakdown. The findings of this research are significant for enhancing the performance of MoS2-based photodetectors and optimizing their stability and reliability in high-power, short-wavelength laser applications.

Optical effects in unmagnetized cold plasmas by a chiral axion factor

Abstract Unmagnetized cold plasma modes are investigated in the context of the chiral Maxwell-Carroll-Field-Jackiw (MCFJ) electrodynamics, where the axion chiral factor acts retrieving some typical properties of magnetized plasmas. The Maxwell equations are rewritten for a cold, uniform, and collisionless fluid plasma model, allowing us to determine the dispersion relation, new refractive indices, and propagating modes. We find four distinct refractive indices modified by the purely timelike CFJ background that plays the magnetic conductivity chiral parameter role associated with right-circularly polarized (RCP) and left-circularly polarized (LCP) waves. For each refractive index, the propagation and absorption zones are determined and illustrated for some specific parameter values. Modified RCP and LCP helicons are found in the low-frequency regime. The optical behavior is investigated, revealing that the chiral factor induces birefringence, measured in terms of the rotatory power (RP). The dichroism coefficient is carried out for the absorbing zones. The negative refraction zones may enhance the involved RP, yielding RP sign reversion, a feature of rotating plasmas and MCFJ chiral plasmas. Charge density oscillations and Langmuir waves are also discussed, revealing no modified dispersion relation due to the chiral axion factor.

Wakefield generation via propagation of two-color asymmetric laser pulses in plasma

Abstract This paper deals with the evolution of longitudinal wakefields generated behind two-color asymmetric laser pulses through homogeneous plasma, using numerical model. The two laser pulses are linearly polarized and are assumed to have frequency difference equal to the plasma frequency. Laser pulses are either positively skewed or negatively skewed with respective asymmetric parameters. Combinations of asymmetric parameters are varied for two laser pulses to optimize the amplitude of wakefield. Maximum enhancement of wake amplitude is reported when both asymmetric laser pulses are positively skewed. Further, particle-in-cell simulations have been performed using Vsim code. The simulation study validates the results obtained wakefields obtained are via numerical model.

Estimating quasi-linear diffusion coefficients for varying values of density ratio

This paper considers a method for estimating bounce-averaged quasi-linear diffusion coefficients due to whistler-mode waves for a specified ratio of plasma frequency to gyrofrequency, ωp/Ωe, using values precomputed for a different value of that ratio. This approach was recently introduced to facilitate calculations associated with the “POES technique,” generalized to infer both wave intensity and cold plasma density from measurements of particle fluxes near the loss cone. The original derivation was justified on the basis of parallel-propagating waves but applied to calculations with much more general models of the waves. Here, we justify the estimates, which are based on equating resonant frequencies for differing values of ωp/Ωe and energy, for wide ranges of wave normal angle, resonance number, energy, and equatorial pitch angle. Refinements of the original estimates are obtained and tested numerically against full calculations of the diffusion coefficients for representative wave models. The estimated diffusion coefficients can be calculated rapidly and generally give useful estimates for energies in the 30-keV–300-keV range, especially when both relevant values of the ratio ωp/Ωe are large.

Electronic, Structural, Optical and Mechanical Properties of Cubic Structured Ln2X3 (Ln = La→Lu & X=O,S): An Empirical Investigation

In this publication, we have examined the structural, optical, and mechanical features of cubic structured lanthanide Ln2X3 (Ln = La→ Lu and X = O, S) series using the valence electron plasma oscillation theory of solids. Using the Chemical bond theory of solids, which was created by Phillips and Van-Vechten, we have further confirmed our findings. Unfortunately, it has been discovered that the Phillips and Van-Vechten (PVV) dielectric description is applicable exclusively to semiconductors and insulators. It is shown that an empirical relationship previously presented by Yadav and Bhati [D.S. Yadav, J. Alloys and Comp. 537, 250 (2012); D.S. Yadav, and D.V. Singh, Phys. Scr. 85, 015701 (2012); D.S. Yadav, J. Mater. Phys. Chem. 3(1), 6-10 (2015); R. Bhati, et al., Mater. Phys. Mech. 51, 90 (2023); R. Bhati, et al., East Eur. J. Phys. (1), 222 (2023).] relating the plasmon energy of complex structured solids, rock salt, and zinc-blende to their electronic, mechanical, static, and dynamical properties which can be applied to the cubic structured lanthanide (Ln2S3 & Ln2O3) series with only minor modifications. Considering the well-known theory of dielectric for solids, an alternative technique has been devised to evaluate the electronic, structural, mechanical, and optical properties of these materials, including their band gap (∆Eg in eV), optical dielectric constant, homopolar and heteropolar gaps, average energy gaps, chemical bond ionicity, and bulk muduli. An estimate was computed based on the almost inverse relationship between the plasmon energy of these compounds and their optical, mechanical, structural, and electrical characteristics. For these substances, the expected values of the aforementioned parameters form a straight line when plotted on a log-log scale against the plasmon energy (ħωp). We examined the C‑type Ln2X3 compounds using the recommended methods, and the values we estimated are in good agreement with the values obtained from modified PVV theory and other comparable experimental and theoretical data that is currently available.

Elastic Properties of C-Type Lanthanide Sesquioxides

In this study, we have presented the solid-state theory of plasma oscillations to investigate the anisotropic elastic properties such as three independent static elastic stiffness constants (Cij: C11, C12 & C44) of C-type Ln2O3 lanthanide solids. The calculated values of the static elastic stiffness constants of Ln2O3 are in excellent agreement with the theoretical results obtained by using ab-initio techniques. The values of elastic stiffness constants (Cij) exhibit a linear relationship when plotted against their plasma energies and lie on a straight line. To further examine the validity of the present estimations on elastic moduli and other parameters of these materials. The mechanical moduli such as bulk modulus (B), shear modulus (G), Young modulus (E), Poisson’s ratio (ν), shear wave constant (Cs), Cauchy pressure (C*), Lame’s coefficient (λ and µ), Kleinman parameter (ξ) Grunesien parameter (γ), Zener anisotropic constant (Z) and Pugh ratio (G/B) of lanthanide solids have also been investigated. For the lanthanide sesquioxide materials, the values of static elastic stiffness constants Cij and elastic moduli were presented for the first time. Unfortunately, in the current study, for many parameters of these materials, experimental results were not found for a comparison with our theoretical predictions. Our estimations agree well with the available experimental data and other theoretical reports.

Effect of annealing temperature onto physical properties of Cu doped ZnO thin films prepared using spray pyrolysis

Abstract Herein we report the effect of annealing on spray-pyrolysis-deposited Cu-doped zinc oxide thin films, with a fixed 3 wt% copper concentration and annealing temperatures of 450 and 500 °C. Various analytical techniques were employed to evaluate the effect of annealed films, which exhibited high stability in physical properties and minimal influence from the annealing process. XRD analysis confirmed that all films maintained a hexagonal ZnO structure without any additional phases, indicating the high purity of the films, with the (002) peak serving as the main diffraction peak for both as-deposited and annealed films. Crystallite size, calculated using the Halder-Wagner equation, revealing an increase from 13.96 nm for the as-deposited film to 14.26 nm for film annealed at 450 °C and 14.65 nm for film annealed at 500 °C. Microstrain values were measured at 2.3 × 10−3, 2.5 × 10−3, and 1.3 × 10−3 for the as-deposited and annealed films. Surface imaging with FE-SEM revealed average grain sizes of 57.25 nm, 68 nm, and 67.8 nm for the as-deposited film and those annealed at 450 °C and 500 °C, respectively. The estimated band gap values were 3.14 eV for the as-deposited films, 3.15 eV for those annealed at 450 °C, and 3.16 eV for films annealed at 500 °C. According to the Spitzer-Fan model, both the density of states and plasma frequency remained constant across the films, while the relaxation time and optical mobility were lowest at 450 °C, where the high-frequency dielectric constant reaches its peak.