Plasma Frequency Research Articles

The Dayside Ionosphere of Mars as Controlled by the Interplay Between Solar Wind Dynamic Pressure and Crustal Magnetic Field Strength.

We investigate how the Martian dayside ionospheric structure is modified by crustal magnetic field (CMF) strength and upstream solar wind pressure by analyzing electron density data from the Langmuir Probe and Waves instrument onboard the MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft. We find that the electron density above the exobase is anticorrelated with the ratio of solar wind's normal dynamic pressure ( ) to CMF magnetic pressure ( ). We also analyze the electron density behavior across different magnetic topologies as a function of . The extremely low electron density in the draped topology relates to ionopause-like structures. The lower electron density in the closed and open topology under higher may be attributed to a downward force, potentially the J×B force in the case of closed topology. This study highlights the complex interplay between solar wind and CMF in influencing the Martian dayside upper ionosphere.

On Plane Oscillations of the Cold Plasma in a Constant Magnetic Field

On Plane Oscillations of the Cold Plasma in a Constant Magnetic Field

Physical properties and thermal stability of zirconium platinum nitride thin films

Ternary transition metal nitrides (TMNs) promise to significantly expand the material design space by opening new functionality and enhancing existing properties. However, most systems have only been investigated computationally, and limited understanding of their stabilizing mechanisms restricts translation to experimental synthesis. To better elucidate key factors in designing ternary TMNs, we experimentally fabricate and analyze the physical properties of the ternary Zr–Pt–N system. Structural analysis and density functional theory modeling demonstrate that Pt substitutes nitrogen on the nonmetallic sublattice, which destabilizes the rock salt structure and forms a complex cubic phase. We also show insolubility of Pt in the Zr–Pt–N at 45 at. % with the formation of a secondary Pt-rich phase. The measured reduced plasma frequency, decrease in resistivity, and decrease in hardness reflect a dominance of metallic behavior in bonding. Additionally, we observe the exsolution of Pt nano precipitates from the Zr–Pt–N films upon annealing as well as degradation in the nitridic film's thermal stability. Even at low concentrations (1%), Pt facilitates a solid reaction with the Si substrate that is otherwise inaccessible in ZrN films.

Electron confinement-induced plasmonic breakdown in metals.

Plasmon resonance represents the collective oscillation of free electron gas density and enables enhanced light-matter interactions in nanoscale dimensions. Traditionally, the classical Drude model describes plasmonic excitation, wherein plasma frequency exhibits no spatial dispersion. Here, we show conclusive experimental evidence of the breakdown of plasmon resonance and a consequent metal-insulator transition in an ultrathin refractory plasmonic material, hafnium nitride (HfN). Epitaxial HfN thick films exhibit a low-loss and high-quality Drude-like plasmon resonance in the visible spectral range. However, as the film thickness is reduced to nanoscale dimensions, Coulomb interaction among electrons increases because of electron confinement, leading to the spatial dispersion of plasma frequency. With a further decrease in thickness, electrons lose their ability to shield the incident electric field, turning the medium into a dielectric. The observed metal-insulator transition might carry some signatures of Wigner crystallization and indicates that such transdimensional, between 2D and 3D, films can serve as a promising playground to study strongly correlated electron systems.

Multifunctional hybrid plasmonic gates using the effect of voltage on the surface plasmons frequency change

Development of plasmonic technology has accelerated in recent years, especially considering the benefits of reducing the scattering limit on bends and low losses as well as the small elemental size. In this paper, the effect of voltage application on changing the frequency of surface plasmons is investigated. Our hybrid device controls light sources using electric voltage. By applying an external voltage to the metal plates and creating a magnetic field, the density of the electrons on the metal surface changes; thus, surface plasmons resonance frequency shifts. To this end, a multifunctional plasmonic gate with a dimension of 95 nm × 95 nm was designed and simulated to evaluate this effect. This structure is suitable for use as AND, NOR, NOT, XOR, and NAND gates. The contrast ratio between the change of state from logic “0” to logic “1” is approximately 29 dB, and the transfer ratio (transmittance ratio) of output in logic “1” is over 85%. The proposed device has low dimensions, a high contrast ratio, and a high transmittance ratio. This device uses four gates: AND, NOR, NOT, XOR, and NAND, which can be achieved in plasmonic integrated circuits with the wavelength division multiplexing (WDM) technique.

Radial Distribution of Electron Quasi-thermal Noise in the Inner Heliosphere

The electron population in the solar wind plasma can be described with three different components: a core, a halo, and a magnetic field aligned strahl. The electron quasi-thermal noise (QTN) is investigated by using an electron population model consisting of a core with a Maxwellian distribution and a halo with a kappa distribution, based on the empirical equations for electron density and temperature and the index for the kappa halo. The power spectra of the electron QTN are calculated at different heliocentric radial distances from 10 to 200 R s . The dependence of the QTN spectrum and effective Debye length on model parameters, including the ratio of the halo to the core for the density and temperature, the kappa index, and the antenna length, is further discussed. The results show that the electron QTN spectrum consists of a plateau in the low-frequency band f < f pt , a peak at the total plasma frequency f pt , and a rapidly decreasing part in the high-frequency band f > f pt . The QTN peak and plateau level continuously decrease as the radial distance increases, with the peak’s shape changing due to the variation of the kappa index. Although the model parameters are variable, the QTN plateau level presents less than an order of change with these parameters changing greatly, and only a monotonic change of the plateau is shown when the parameters are close to the practical situation. The results can provide a reference for future deep-space exploration in the inner heliosphere, and also for the design of detectors.

Laboratory Simulations of Plasma Generated Around the Atmospheric Reentry Spacecraft

In this paper, plasma will be generated in a laboratory as a simulation of what happens to spacecraft when they enter the atmosphere of Earth. Parameters of plasma generation were determined in terms of pressures of 0.1, 0.2, 0.3, 0.4, and 0.5 mbar and generation energy 200 W. The parameters of the generated plasma were calculated using the optical emission spectroscopy two intensity ratio method, and the electron temperature, electron density, Debye length, and plasma frequency were calculated. Compare the results with the actual results, electron temperatures were 2.26–1.71 eV and plasma frequency 8.09 x1011-6.7x1011 at 0.1-0.5 mbar pressure.

Resonant conversion of axion dark radiation into terahertz electromagnetic radiation in a neutron star magnetosphere

In the strong magnetic field of a neutron star’s magnetosphere, axions coupled to electromagnetism develop a nonzero probability to convert into photons. Past studies have revealed that the axion-photon conversion can be resonantly enhanced. We recognize that the axion-photon resonance admits two parametrically distinct resonant solutions, which we call the mass-matched resonance and the Euler-Heisenberg assisted resonance. The mass-matched resonance occurs at a point in the magnetosphere where the radially-varying plasma frequency crosses the axion mass ωpl≈ma. The Euler-Heisenberg assisted resonance occurs where the axion energy satisfies ω≈(2ωpl2/7gγγγγB¯2)1/2. This second resonance is made possible though the strong background magnetic field B¯, as well as the nonzero Euler-Heisenberg four-photon self-interaction, which has the coupling gγγγγ=8α2/45me4. We study the resonant conversion of relativistic axion dark radiation into photons via the Euler-Heisenberg assisted resonance, and we calculate the expected electromagnetic radiation assuming different values for the axion-photon coupling gaγγ and different amplitudes for the axion flux onto the neutron star Φa. We briefly discuss several possible sources of axion dark radiation. Achieving a sufficiently strong axion flux to induce a detectable electromagnetic signal seems unlikely. Published by the American Physical Society 2024

Ultrafast terahertz conductivity in epitaxial graphene nanoribbons: an interplay between photoexcited and secondary hot carriers

Abstract Optical pump-terahertz probe spectroscopy has been used to investigate ultrafast photo-induced charge carrier transport in 3.4 µm wide graphene ribbons upon scaling the optical pump intensity. For low pump fluences, the deposited pump energy is rapidly redistributed through carrier–carrier scattering, producing secondary hot carriers: the picosecond THz photoconductivity then acquires a negative sign and scales linearly with an increasing pump fluence. At higher fluences, there are not enough equilibrium carriers able to accept the deposited energy, directly generated (excess) carriers start to contribute significantly to the photoconductivity with a positive sign leading to its saturation behavior. This leads to a non-monotonic variation of the carrier mobility and plasmonic resonance frequency as a function of the pump fluence and, at high fluences, to a balance between a decreasing carrier scattering time and an increasing Drude weight. In addition, a weak carrier localization observed for the polarization parallel to the ribbons at low pump fluences is progressively lifted upon increasing the pump fluence as a result of the rise of initial carrier temperature.

Analysis of uncertainty in measurement of electron temperature in low-pressure inductively coupled plasmas using microwave cutoff probe

Abstract In this study, we performed electron temperature measurements by using a square cutoff probe. Further, the measurement uncertainty was comprehensively analysed. The square cutoff probe allows for the measurement of the electron temperature based on the measured electron series resonance frequency and that of the electron plasma frequency based on the transmission spectrum of the plasma. The electron temperatures were determined under varying gas pressures and input power conditions, and the results were compared with those obtained using a single Langmuir probe. Also, the impact of electron-neutral collision frequency on electron temperature measurement using square cutoff probe was analyzed based on a plasma equivalent circuit model. The square cutoff probe is expected to serve as a valuable diagnostic tool for the precise characterisation of electron temperature, offering localised, accurate, and easily interpretable features.

Precisely tuning ε′-negative and ε′-near-zero responses by synergistic effect of graphene and carbon black in ternary metacomposites

Understanding how to precisely regulate the magnitude and dispersion characteristics of radio-frequency (RF) ε’-negative and ε’-near-zero (ENZ) responses presents a challenge. This challenge significantly impacts the design of versatile electronic devices. In this study, we introduce a synergistic strategy utilizing graphene (GR) and carbon black (CB) in ternary metacomposites for tunable ε’-negative and ENZ responses. Due to the randomly constructed 3-dimensional (3D) conductive GR-CB networks in a CaCu3Ti4O12 matrix, we observed two types of ε’-negative response mechanisms: electric dipole resonance and low-frequency plasma oscillation, which dominate at different frequency bands. Consequently, the weakly ε’-negative values (0 < |ε’| 〈1000) and frequency dispersion were successfully adjusted due to the interplay between these two mechanisms. The ENZ frequencies were also tuned over ∼580 MHz, 225 MHz, ∼189 MHz and ∼ 188 MHz with variable GR-to-CB ratios. Furthermore, we studied the conduction behavior, loss mechanism, and electrical characteristics of the ε’-negative metacomposites to shed light on the relationship between microstructural changes and dielectric performance.

Josephson traveling wave parametric amplifiers with plasma oscillation phase matching

High gain and large bandwidth of traveling-wave parametric amplifier exploiting the nonlinearity of Josephson Junctions can be achieved by fulfilling the so-called phase-matching condition. This condition is usually addressed by placing resonant structures along the waveguide or by periodic modulations of its parameters, creating gaps in the waveguide’s dispersion. Here, we propose to employ the Josephson junctions, which constitute the centerline of the amplifier, as resonant elements for phase matching. By numerical simulations in JoSIM (and WRspice) software, we show that Josephson plasma oscillations can be utilized to create wave vector mismatch sufficient for phase matching as well as to prevent the conversion of the pump energy to higher harmonics. The proposed traveling wave parametric amplifier design has a gain of 15 dB and a 3 GHz bandwidth, which is comparable to the state-of-the-art TWPAs.

Buckling-induced variations in electronic, thermal, and optical properties of B[formula omitted]C[formula omitted]N[formula omitted] monolayer: DFT and AIMD computational approaches

Density functional theory is employed to study the novel properties of B3C2N3 monolayer to gain a deeper understanding of variation of electronic, thermal, and optical characteristics arising due to buckling effects. The band structure analysis reveals an energy gap reduction of the buckled B3C2N3 monolayer, causing a displacement of the band gap from the visible to the infrared range. Moreover, the buckling controls the location of the initially, and finally, direct band gap moving it from the K to the Γ point in the B3C2N3 monolayer. The phonon band structure calculations indicate that buckled B3C2N3 monolayers are dynamically stable, while ab-initio molecular dynamics simulations, AIMD, evaluate and confirm the thermal stability of both flat and buckled B3C2N3 monolayers. The buckling phenomenon at low temperatures has no a significant impact on the heat capacity contrary to what happens in the high temperature limit. The optical characteristics of the B3C2N3 monolayer, including refractive index, optical conductivity, static dielectric function, and plasmon frequency, are evaluated at different levels of the buckling parameter. The static dielectric function and plasmon frequency are enhanced with the buckling due to the screening of the electron–electron interactions, affecting the collective oscillations. Enhanced screening gives rise higher plasmon frequencies. Tuning the buckling parameter illustrates the significance of buckling as an alternative mechanism for adjusting the performance of B3C2N3 two-dimensional materials for different technological applications such as solar and optoelectronic systems.

A new approach to the description of plasma Langmuir waves

After finding an exact solution to the Vlasov–Boltzmann kinetic equation (i.e., finding distribution functions for plasma particles), we consider the description of Landau damping using Poisson's equation, since with the complete distribution function, there is no need to split the kinetic equation into equilibrium and perturbed parts for the subsequent implementation of the pole bypass in the integrand expression. The found distribution function depends, in addition to velocity, on the coordinates and can be used to analytically consider different cases and configurations of the spatial confinement of the plasma. General distribution function for electrons is discussed. We consider the behavior of Langmuir waves, also at the nonlinear stage.

Statistical Properties of Quasi‐Periodic Electromagnetic Ion Cyclotron Waves: ULF Modulation Effects

AbstractElectromagnetic ion cyclotron (EMIC) waves effectively scatter relativistic electrons in Earth's radiation belts and energetic ions in the ring current. Empirical models parameterizing the EMIC wave characteristics are important elements of inner magnetosphere simulations. Two main EMIC wave populations included in such simulations are the population generated by plasma sheet injections and another population generated by magnetospheric compression due to the solar wind. In this study, we investigate a third class of EMIC waves, generated by hot plasma sheet ions modulated by compressional ultra‐low frequency (ULF) waves. Such ULF‐modulated EMIC waves are mostly observed on the dayside, between magnetopause and the outer radiation belt edge. We show that ULF‐modulated EMIC waves are weakly oblique (with a wave normal angle ) and narrow‐banded (with a spectral width of of the mean frequency). We construct an empirical model of the EMIC wave characteristics as a function of ‐shell and MLT. The low ratio of electron plasma frequency to electron gyrofrequency around the EMIC wave generation region does not allow these waves to scatter energetic electrons. However, these waves provide very effective (comparable to strong diffusion) quasi‐periodic precipitation of plasma sheet protons.

Observation of self-excited oscillations in DC glow discharge dusty plasma

We present a detailed experimental study of discharge current oscillations in a planar cathode plasma with poly dispersed alumina dust particles. Our experimental measurements suggest that surface density of dust particles play an important role together with cathode spots, in deciding self excited oscillating regime or stable dust cloud regime. Experiments conducted with dust particles density below the critical limit shows self excited oscillations. Operating above the critical limit, a dust cloud levitated in the sheath region was observed.

The frequency spectrum and energy content in a pulse flux of terahertz radiation generated by a relativistic electron beam in a plasma column with different density distributions

This paper reports on the generation of a directed flux of electromagnetic radiation with an energy content of 10 J in the frequency range of 0.2—0.3 THz at a microsecond pulse duration in a beam-plasma system. The flux is generated when a relativistic electron beam (REB) pumps electron plasma waves in a magnetized plasma column. In the described experiments, this fundamentally new approach to generate terahertz radiation was carried out at the GOL-PET facility in the conditions of varying the beam current density and the plasma density in the appropriate ranges of 1—2 kA/cm2 and 1014—1015 cm−3. From the comparison of the flux energy spectrum measured experimentally in the frequency range 0.15—0.45 THz with the calculated one obtained using the previously proposed model of radiation generation in a beam–plasma system, it was shown that this process occurs through resonant pumping by REB of precisely the branch of upper-hybrid plasma waves. Mastering this new method to generate terahertz radiation opens the prospect of its use to obtain multi-megawatt radiation fluxes in the frequency range up to 1 terahertz and higher. For such a development approach the most promising beam for pumping plasma oscillations seems to be a kiloampere REB generated in a linear induction accelerator.

Impulsively Accelerated Ions as the Source of Ion Acoustic Waves in Solar Wind

Ion acoustic waves are pervasive at the Earth’s bow shock and in regions of active plasmas. Recently, frequency-dispersed ion acoustic-like waves have been observed by Parker Solar Probe in the near-Sun solar wind. These waves are electrostatic, propagate nearly along the magnetic field, and have frequencies on the order of the ion plasma frequency. Frequency-dispersed emissions appear in short (<1 s) bursts and exhibit rising and/or falling tones. This article has a narrow focus, to determine if impulsively accelerated ions are a plausible generation mechanism. We show that velocity dispersion from impulsively accelerated ions can generate a positive slope in the ion distribution that changes in space and time, which can lead to emissions with rising or falling tones given a substantial Doppler shift from the solar wind. The phase velocity is at the velocity of the positive slope, which can differ from the ion acoustic speed, but otherwise these waves are similar to ion acoustic waves. Wave growth is strongest when the positive slope velocity is near the ion acoustic speed. Two mechanisms for impulsive ion acceleration are explored. One mechanism imparts equal energy into the source ions as expected from a parallel potential. The other mechanism imparts equal velocity into the source ions such as that expected from impulsive magnetic reconnection. Both mechanisms result in similar wave characteristics with only subtle differences. Given the persistent appearance of these ion acoustic-like waves, these results suggest that impulsively accelerated ions may be abundant in the near-Sun solar wind.

Absorption of electromagnetic waves by cylindrical surface plasmon resonance

Abstract The absorption characteristics of cylindrical surface plasmon resonance (CSPR) have been studied. We demonstrated that a single plasma column with CSPRs can achieve high absorptivity at the plasmon frequency. We also studied the effects of plasma density and collision frequency on the absorptivity. As both of them increase, the corresponding absorptivity tends to increase first and then decrease, but with different reasons. Such manifestation is explained by analyzing transmission and reflection spectra in both cases, as well as magnetic field distribution patterns at the frequency of plasmon. On the one hand, the increase in plasma density leads to the enhancement of plasmons, improving transmittance; On the other hand, the increase in collision frequency leads to a weakening of plasmons and an increase in reflectivity. Finally, we investigated the absorption characteristics of plasmons in the plasma photonic crystals (PPCs) structure and overcame the absorption attenuation caused by the increase in plasma density by increasing the number of plasma columns. Meanwhile, the absorption generated by surface plasmon resonance is not affected by the lattice constant of PPCs. The research has shown that efficient absorption can be achieved using CSPR, resulting in extremely high absorptivity when using fewer plasma columns. Finally, we verified the absorption ability of CSPRs through experiments.

Plasma antenna with frequency adjustment

A discharge of limited length (“plasma column”) in a gas-discharge tube filled with a rarefied gas was studied. The discharge is created due to the one-sided excitation of an extended high-frequency discharge supported by a propagating azimuthally symmetric mode of the surface wave. It is shown that a “plasma column” can be an effective plasma antenna at operating frequencies below the plasma frequency (ωp), with frequency tuning due to changes in the length of the “plasma column”.