Electron Number Density Profiles Research Articles

Investigating the Nature of Plasma Oscillations in Cold Plasma

Plasma oscillations are one of the important phenomena in plasma. The research in the field of plasma oscillation has a long history for more than six decades. The cold plasma is one in which electron temperature is very large but the neutral atoms are at room temperature. This study aims to obtain electron number density, electric field and velocity profile in cold plasma. Analytical method has been used to conduct this study. Fluid equations were solved to get the solution for number density, electric field and velocity of electron. To get the solution, first fluid equations are transferred to Lagrangian co-ordinates, where equations become linear and expression for respective parameter was obtained. A sinusoidal perturbation was taken as an initial condition and solution for number density; electric field and velocity were obtained. Value of perturbation was varied and corresponding waveforms were achieved and analyzed. As the perturbation increases the wave amplitude also increased. It is found that as the perturbation value is there is wave breaking in number density profile. Unlike in the number density, no such wave breaking is obtained for electric field and velocity profile. However the amplitude of waveform of electric field and velocity profile found to increases with increase in perturbation level.

Modeling of argon–steam thermal plasma flow for abatement of fluorinated compounds

This study presents a numerical model of the hybrid-stabilized argon–steam thermal DC plasma torch of a new design for generating an argon–steam plasma suitable for efficient abatement of persistent perfluorinated compounds. The model includes the discharge region and the plasma jet flowing to the surrounding steam atmosphere contained in a plasma-chemical chamber. Compared to previous studies, the torch had a smaller nozzle diameter (5.3 mm) and a reduced input power (20–40 kW) and arc current (120–220 A). The outlet region for the plasma jet extends to 20 cm downstream of the exit nozzle. Fluid dynamic and thermal characteristics together with diffusion of argon, hydrogen and oxygen species, and distribution of plasma species in the discharge and the plasma jet are obtained for currents from 120 to 220 A. The results of the calculations show that the plasma jet exhibits high spatiotemporal fluctuations in the shear layer between the plasma jet and colder steam atmosphere. The most abundant species in the plasma jet are hydrogen and oxygen atoms near the jet center, and molecules of H2, O2 and OH in colder surrounding regions. Satisfactory agreement is obtained with measurements of the radial temperature and electron number density profiles near the jet center close to the nozzle exit.

Atacama Cosmology Telescope: Combined kinematic and thermal Sunyaev-Zel’dovich measurements from BOSS CMASS and LOWZ halos

The scattering of cosmic microwave background (CMB) photons off the free-electron gas in galaxies and clusters leaves detectable imprints on high resolution CMB maps: the thermal and kinematic Sunyaev-Zel'dovich effects (tSZ and kSZ respectively). We use combined microwave maps from the Atacama Cosmology Telescope (ACT) DR5 and Planck in combination with the CMASS and LOWZ galaxy catalogs from the Baryon Oscillation Spectroscopic Survey (BOSS DR10 and DR12), to study the gas associated with these galaxy groups. Using individual reconstructed velocities, we perform a stacking analysis and reject the no-kSZ hypothesis at 6.5$\sigma$, the highest significance to date. This directly translates into a measurement of the electron number density profile, and thus of the gas density profile. Despite the limited signal to noise, the measurement shows at high significance that the gas density profile is more extended than the dark matter density profile, for any reasonable baryon abundance (formally $>90\sigma$ for the cosmic baryon abundance). We simultaneously measure the tSZ signal, i.e. the electron thermal pressure profile of the same CMASS objects, and reject the no-tSZ hypothesis at 10$\sigma$. We combine tSZ and kSZ measurements to estimate the electron temperature to 20% precision in several aperture bins, and find it comparable to the virial temperature. In a companion paper, we analyze these measurements to constrain the gas thermodynamics and the properties of feedback inside galaxy groups. We present the corresponding LOWZ measurements in this paper, ruling out a null kSZ (tSZ) signal at 2.9 (13.9)$\sigma$, and leave their interpretation to future work. Our stacking software ThumbStack is publicly available at https://github.com/EmmanuelSchaan/ThumbStack and directly applicable to future Simons Observatory and CMB-S4 data.

Electron density profile inside a cylindrical plasma with elliptical cross section in a microwave discharge

In a microwave discharge, the profile of electron number density inside a cylindrical plasma with elliptic cross section is analytically calculated. Using separation of variables way for the electron continuity equation (as function of position and time) and so solving it, the electron number density profile is calculated. It is shown that the profile of electron number density in a cylindrical plasma with elliptical cross section is in the form of Mathieu functions. The characteristic diffusion length for the elliptical cylinder plasma is obtained, and it is seen that it is different with the characteristic diffusion length for the circular cylinder plasma. In the steady state, the normalized density profiles of lowest even and odd modes are plotted. Furthermore, the components of normalized electron number density gradient are plotted. In the limit that plasma cylinder with elliptical cross section being converted to plasma cylinder with circular cross section, the obtained results are confirmed.

Suzaku Measurements of Hot Halo Emission at Outskirts for Two Poor Galaxy Groups: NGC 3402 and NGC 5129

Abstract We present Suzaku off-center observations of two poor galaxy groups, NGC 3402 and NGC 5129, with temperatures below 1 keV. Through spectral decomposition, we measured their surface brightnesses and temperatures out to 530 and 1430 times the critical density of the universe for NGC 3402 and NGC 5129, respectively. These quantities are consistent with extrapolations from existing inner measurements of the two groups. With the refined bolometric X-ray luminosities, both groups prefer L X–T relations without a break in the group regime. Furthermore, we have determined the electron number densities and hydrostatic masses at these radii. We found that the surface brightness and electron number density profiles require two β model components, as well as the indication that a third β model may be needed for NGC 3402. Adding the gas mass measured from the X-ray data and stellar mass from group galaxy members, we computed baryon fractions of f b =0.0693 ± 0.0068 and f b = 0.095 ± 0.014 for NGC 3402 and NGC 5129, respectively. Combining other poor groups with well-measured X-ray emission to the outskirts, we found an average baryon fraction extrapolated to r 500 of = 0.0912 ± 0.0050 for X-ray-bright groups with temperatures between 0.8 and 1.3 keV, extending existing constraints to lower-mass systems and indicating that significant baryon losses exist below approximately r 500.

Analysis of Electromagnetic Wave Propagation in Unmagnetized Hypersonic Vehicle Plasma Sheath Using the Variational Method

The propagation of electromagnetic waves in the plasma sheath is investigated theoretically and numerically using the variational method, which handles the inhomogeneity of the plasma sheath. We derive the variation of the action integral, which can be numerically represented by expanding the velocity and electromagnetic fields to the piecewise polynomial function space. We analyze the transmissivity of electromagnetic waves propagating through the plasma sheath with the barrier and the barrier-parabolic electron number density profile. We give the frequency-dependent transmissivity of electromagnetic wave propagation in different inhomogeneous plasma sheaths. The electromagnetic energy density derived from the Lagrangian density is also given, and the result shows that the collision between electrons and neutral particles can be used to enhance the transmission of electromagnetic waves in the plasma sheath.

The YSZ,Planck – YSZ,XMM scaling relation and its difference between cool-core and non-cool-core clusters

We construct a sample of 70 clusters using data from XMM-Newton and Planck to investigate the YSZ,Planck – YSZ,XMM scaling relation and the cool-core influences on this relation. YSZ,XMM is calculated by accurately de-projected temperature and electron number density profiles derived from XMM-Newton. YSZ,Planck is the latest Planck data restricted to our precise X-ray cluster size θ500. To study the cool-core influences on the YSZ,Planck – YSZ,XMM scaling relation, we apply two criteria, namely the limits of central cooling time and classic mass deposition rate, to distinguish cool-core clusters (CCCs) from non-cool-core clusters (NCCCs). We also use YSZ,Planck from other papers, which are derived from different methods, to confirm our results. The intercept and slope of the YSZ,Planck – YSZ,XMM scaling relation are A = –0.86 ± 0.30 and B = 0.83 ± 0.06 respectively. The intrinsic scatter is σins = 0.14 ± 0.03. The ratio of YSZ,Planck/YSZ,XMM is 1.03 ± 0.05, which is in excellent statistical agreement with unity. Discrepancies in the YSZ,Planck – YSZ,XMM scaling relation between CCCs and NCCCs are found in the observation. They are independent of the cool-core classification criteria and YSZ,Planck calculation methods, although the discrepancies are more significant under the classification criteria of classic mass deposition rate. The intrinsic scatter of CCCs (0.04) is quite small compared to that of NCCCs (0.27). The ratio of YSZ,Planck/YSZ,XMM for CCCs is 0.89 ± 0.05, suggesting that CCCs’ YSZ,XMM may overestimate the Sunyaev-Zel’dovich (SZ) signal. By contrast, the ratio of YSZ,Planck/YSZ,XMM for NCCCs is 1.14 ± 0.12, which indicates that NCCCs’ YSZ,XMM may underestimate the SZ signal.

A kinetic study of electron heating and plasma dynamics in microwave microplasmas

Microwave microplasmas ignited in argon are studied using a one-dimensional particle-in-cell with Monte Carlo collision (PIC-MCC) approach. One-dimensional PIC-MCC simulations are performed at specified input power densities to determine the influence of the applied frequency (ranging from 1 to 320 GHz), pressure, and total deposited power on the plasma dynamics. The frequency response study performed at a fixed input power density shows the presence of off-axis peaks in the electron number density profile at intermediate frequencies. These peaks are attributed to the interplay between the production of hot electrons by the oscillating sheath and their inability to diffuse sufficiently at higher operating pressures, thereby resulting in enhanced ionization at off-axis locations. This is confirmed by the pressure dependence study which shows that the electron number density peaks at the mid-point when the microplasma is ignited at lower pressures. As the excitation frequency is increased further, the sheath oscillation heating decreases and eventually vanishes, thereby requiring the bulk plasma to couple power to the electrons which in turn leads to an increase in electron temperature in the plasma bulk and the electron number density peak appearing at the mid-point. When the power coupled to the microplasma is decreased, the sheath oscillation at a given frequency decreases, thereby leading to higher contribution from heating in the bulk plasma which leads to the disappearance of off-axis peaks even at intermediate frequencies. The microplasma dynamics at all conditions considered in this work demonstrate the interplay between the electron momentum transfer collision frequency, the angular excitation frequency, and the plasma frequency.

The optical depth of gamma radiation due to interaction with the thermal bremsstrahlung of hot gas in galaxy clusters.

The interaction of high energy gamma quantum to thermal bremsstrahlung photons of hot intracluster gas with producing electron-positron pair is considered. It is supposed that galaxy cluster is relaxed and electron number density and temperature profiles are spherical symmetric. The dependence of optical depth on gamma quantum energy and distance to cluster center is considered. It is shown that the optical depth due to considered interaction is about 10−8 − 10−5 at gamma quantum energy 100 MeV - 1 TeV.

Electron number density profiles derived from radio occultation on the CASSIOPE spacecraft

AbstractThis paper presents electron number density profiles derived from high‐resolution Global Positioning System (GPS) radio occultation (RO) observations performed using the Enhanced Polar Outflow Probe payload on the high inclination CAScade, Smallsat and IOnospheric Polar Explorer (CASSIOPE) spacecraft. We have developed and applied a novel inverse Abel transform algorithm on high rate RO total electron content measurements performed along GPS to CASSIOPE radio links to recover electron density profiles. The high‐resolution density profiles inferred from the CASSIOPE RO are (1) in very good agreement with density profiles estimated from ionosonde data, measured over stations nearby to the latitude and longitude of the RO tangent points; (2) in good agreement with density profiles inferred from GPS RO measured by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC); and (3) in general agreement with density profiles estimated using the International Reference Ionosphere climatological model. Using both CASSIOPE and COSMIC RO observations, we identify, for the first time, that there exist differences in the characteristics of the electron number density profiles retrieved over landmasses and oceans. The density profiles over oceans exhibit widespread values and scale heights compared to density profiles over landmasses. We provide an explanation for the ocean‐landmass discrepancy in terms of the unique wave coupling mechanisms operating over oceans and landmasses.

Operating modes of field emission assisted microplasmas in the microwave regime

The operating modes of microwave microplasma devices integrated with field emitting cathodes are studied using one-dimensional particle-in-cell with Monte Carlo collision (PIC-MCC) simulations. The PIC-MCC simulations predict operation in two modes—an α-mode characterized by a positive differential resistance with negligible influence of boundary processes and a γ-mode with significant field-induced electron emission. PIC-MCC results are presented for two representative 0.5 GHz argon microplasmas operating in the α and γ modes. The field emission-induced transition to γ-mode modifies the electron number density profiles in the sheath apart from leading to a higher contribution of conduction current in the sheath. The interpretation of electrical characteristics using time history of voltage and current demonstrates that the microplasma device impedance decreases as a result of the thinner sheath. It is also shown that the presence of field emitting cathodes leads to lower power requirements (about 64% of the case presented without field emission) to achieve a given plasma density.

On the propagation and mode conversion of auroral medium frequency bursts

AbstractAuroral medium frequency (MF) bursts are broadband, impulsive radio emissions associated with local substorm onsets. MF bursts consist of a characteristic fine structure whereby the higher frequencies arrive 10–100 ms before the lower frequencies. LaBelle (2011a) proposed that MF bursts originate as Langmuir/Z mode waves on the topside of the ionosphere that mode‐convert to LO mode waves and propagate to ground level, with the fine structure resulting by propagation delays due to the topside ionospheric density profile. We investigate three aspects of this mechanism. First, full‐wave calculations are used to simulate the MF burst fine structure using a realistic ionospheric density profile. The delay between the highest and lowest frequencies is 21 ms. This value is smaller than the experimentally determined delays of ∼100 ms presented in Bunch and LaBelle (2009), but differences between the topside electron number density profile used in the simulations and the number density profile during disturbed conditions make comparisons only approximate. Second, the Landau damping of Langmuir/Z mode waves on the topside ionosphere is calculated, assuming the electron distribution function consists of a cold background population (ne0) and a warm secondary population (nse). The Landau damping is small when nse/ne0 = 0.04% (consistent with Maggs and Lotko (1981)) but is significant when nse/ne0 > 0.4%. Finally, full‐wave calculations are used to determine the mode conversion efficiency from Langmuir/Z mode waves to LO mode waves. These imply that waves would suffer an attenuation of wave energy density of approximately 5–10% if they are generated with their wave vectors in a narrow cone centered around the local magnetic field. Taken together, these calculations suggest that for small values of nse/ne0 <0.4%, the mechanism proposed by LaBelle (2011a) is a plausible explanation for the origin of MF bursts.

Characteristics of a resonant iris microwave-induced nitrogen plasma

Temperature, electron number density and robustness profiles of a N2plasma contribute for more sensitive and accurate MIP OES determinations.

A tunable microplasma gradient-index lens for millimeter waves

This work presents proof of concept of a novel application of field emission assisted (FEA) microplasmas that exploits the relatively high plasma number densities encountered in these devices. We hypothesize that the number density gradients and the resulting gradient in the microplasma relative permittivity/refractive index can be utilized as a tunable diverging lens with on/off ability to defocus waves in the Terahertz regime. Electron number density profiles obtained from one-dimensional particle-in-cell with Monte Carlo collisions simulations for a typical FEA microplasma are used to determine the relative permittivity and conductivity profiles. Frequency domain wave propagation simulations using these profiles show that sub-mm waves can be controlled using the microplasma lens with the degree of defocusing depending on the wavelength. In spite of the non-zero conductivity, the medium is not significantly lossy at the frequencies considered.

Latitudinal variations and altitude profiles of ionospheric parameters: Comparison of theoretical and empirical model results

Using the global numerical upper atmosphere model (UAM), ionospheric electron density variations have been simulated for different seasons as well as low and high solar activities. The UAM results have been compared with the values obtained with IRI-2012 ionospheric model calculations. It has been shown that the UAM results are consistent with the results obtained by the IRI-2012 empirical model for middle and lower latitudes and daytime hours at both low and high solar activity levels with a discrepancy of up to 40% regardless of the season. The difference between UAM and IRI-2012 values calculated for electron density peaks at high latitudes and can be explained by the fact that the empirical model does not reproduce the main ionospheric trough. In addition, there have been large discrepancies in the altitudinal profiles of electron number density for plasmaspheric heights and low solar activity. This discrepancy can be explained by the influence of initial conditions on numerical simulation results.

Time function triple Langmuir probe measurements in low frequency pulsed DC discharge plasma

This study investigated the temporal profiles of electron temperature and number density in rectified DC air discharge generated with a 50 Hz step-up transformer. An in-house built triple Langmuir probe and circuitry were used to diagnose the plasma parameters as a function of input voltage and filling gas pressure. A tungsten metal wire capable of withstanding the high temperatures was used as probe tip material. The temporal profiles revealed an increase in electron temperature with input voltage in the range of 380 to 450 V, whereas, an inverse relation between number density and input voltage was evident in the given work. The observed trend in the plasma parameters was absolutely reversed in case of the filling gas pressure. The electron temperature linearly decreased with an increase in pressure from 1 to 4 mbar, whereas a linear increase in number density with pressure was seen in the temporal profiles. Finally, it was concluded that the results for the tested plasma parameters were consistent and the in-house built probe functioned well in DC discharge for the used range of voltage and filling pressure.

Prediction of Nonequilibrium Air Plasma Radiation Behind a Shock Wave

The absolute radiation measurements obtained in the electric arc-driven shock-tube facility at NASA Ames Research Center were analyzed to test the collisional-radiative model developed at École Centrale Paris. Two conditions representative of Earth reentry at 10.54 and were investigated in the vacuum ultraviolet and infrared spectral ranges. For each of the conditions, the corresponding charge-coupled device images were analyzed. The electron number density was inferred from Stark-broadened nitrogen and lines. Comparisons with the predicted electron number density profiles enabled us to validate the ionization rate constant model implemented in the flowfield solver and to accurately locate the shock front. For both freestream conditions and all the spectral ranges, the predictions of the initial intensity rises were improved when the total spatial smearing (due to the shock motion, the optics, and the camera) was taken into account. The nonequilibrium intensities observed in the vacuum ultraviolet and infrared spectral ranges were underpredicted by the collisional-radiative model when only electron-impact excitation and ionization processes were taken into account. Then, the effect of heavy-particle impact processes was studied by applying various multitemperature dissociation rate constant and vibration–dissociation coupling models as well as heavy-particle impact excitation models. The nonequilibrium peak intensities observed in the vacuum ultraviolet and infrared spectral ranges were shown to be controlled by heavy-particle impact excitation processes.

基于无线电掩星观测的火星电离层观测研究进展

The early observations of the Mars ionosphere are very limited. Most of the information concerning the ionospheric properties of Mars comes from radio occultation experiments. Recent measurements by Mars Global Surveyor and Mars Express have greatly increased the number of observations of Martian dayside and nightside ionosphere. Large datasets of electron number density profiles have been published online for scientific analysis. Martian ionosphere is influenced by many factors, such as: solar EUV and X ray irradiance, solar wind, solar flare, neutral atmosphere, crustal magnetic field, cosmic rays, meteoric showers and so on. They lead to instantaneous and seasonal variations in Martian ionosphere. In this paper, fundamental principles and features of planetary radio occultation technique are briefly discussed. An introduction of the domestic work concerning the Joint Russia-China Mars exploration (YH-1) is also presented here. New developments in the study of the Martian ionosphere based on radio occultation observations are viewed, mostly from Mars Global Surveyor and Mars Express datasets. The layer structure of Martian dayside ionosphere and factors affecting the variability of each layer are summarized. Here we adopted from Withers, to classify the structure of Martian dayside ionosphere as: M1 below, M1, M2, and M2 above. Some newest findings with regard to the influence of solar activity, neutral atmosphere, crustal magnetic field and meteoric showers on the electron density profile, especially on the peak density and peak height of M2 and M1 layers are presented. This paper also discusses the variation mechanisms and the recent studies of Martian nightside ionosphere. The future research topics of Martian ionosphere will be centered on the interactions of the solar wind and the upper atmosphere, ion loss at Mars, the crustal magnetic control of local ionosphere, structure of night ionosphere and so on.

Neutrino luminosity and matter-induced modification of collective neutrino flavor oscillations in supernovae

We present the first calculations of self-coupled neutrino flavor oscillations with time integrated luminosities and energy spectra for the neutronization burst of an $\mathrm{O}\ensuremath{-}\mathrm{Ne}\ensuremath{-}\mathrm{Mg}$ core-collapse supernova. These calculations allow us to gauge the effects of time varying neutrino luminosity and of the bump in the electron number density profile at the base of the hydrogen envelope in $\mathrm{O}\ensuremath{-}\mathrm{Ne}\ensuremath{-}\mathrm{Mg}$ core-collapse supernovae. The bump allows a significant fraction of the low-energy ${\ensuremath{\nu}}_{e}$ to survive by rendering their flavor-evolution nonadiabatic. Increasing the luminosity of the neutronization burst shifts the bump-affected ${\ensuremath{\nu}}_{e}$ to lower energy with reduced survival probability. Similarly, lowering the luminosity shifts the bump-affected neutrinos to higher energies. While these low-energy neutrinos lie near the edge of detectability, the population of bump-affected neutrinos has direct influence on the spectral swap formation in the neutrino signal at higher energies.

Numerical Simulation of Electron Transport in Electric and Magnetic Fields for Analysis of Electron Temperature and Number Density Profiles Measured in Argon Magnetic Neutral Loop Discharge Plasma

A Monte Carlo simulation of electron transport in electric and magnetic fields was performed to analyze experimental data of the electron temperature Te and electron number density ne measured in a magnetic neutral loop discharge (NLD) plasma driven in Ar at 0.13 Pa. Te and ne in the vicinity of the substrate holder were measured with a triple probe, and their radial profiles had peaks at different radial positions. The simulation reproduced these peak positions well under the chosen boundary condition that the electron reflectivity of the side wall was lower than that of the reactor ceiling and the substrate holder. It was explained that the Te peak was formed by high-energy electrons transported from the neutral loop along a separatrix of the quadrupole magnetic field and that the ne peak consisted of electrons undergoing reciprocating motion between the reactor ceiling and the substrate.