Variation Of Electron Density Research Articles

Multi‐instrumental Observations of the Quasi‐16‐Day Variations From the Lower Thermosphere to the Topside Ionosphere in the Low‐Latitude Eastern Asian Sector During the 2017 Sudden Stratospheric Warming Event

AbstractVariations of the low‐latitude ionosphere in the eastern Asian sector during the 2017 sudden stratospheric warming (SSW) were studied with multi‐instrumental observations that correspond to different altitudes. Specifically, the variations of the topside ionosphere as high as over 830 km were investigated with data from the Swarm B satellite (~500 km), the Defense Meteorological Satellite Program F15 satellite (~830 km), and the Meteorological Operational satellite‐A (~830 km). The main results are as follows. (1) Simultaneous variations were detected in the ionospheric parameters from the E region to the topside ionosphere around the first peak warming of the 2017 SSW. (2) These variations exhibited similar quasi‐16‐day (Q16D; ~14.5‐day) periods, and these periods were most significant just before the first peak warming. (3) These simultaneous Q16D variations were not due to the solar extreme ultraviolet irradiance or geomagnetic activities but were probably driven from below, by planetary waves or semidiurnal lunar tides that enhanced during the SSW. (4) The Q16D variation of the topside ionospheric electron density at ~830 km was probably driven not only by the upward mapping electric field modulated in the E region dynamo but also by the electric field modulated in the F region dynamo.

A novel antenna for sub‐atmospheric radio‐frequency discharge

AbstractA novel antenna that can generate plasma efficiently for pressure up to thousands of Pascal with 1 kW–13.56 MHz radio‐frequency power supply is reported. It consists of two isolated solenoids so that involves both capacitively coupling and inductively coupling effects, together with magnetic mirror effect which confines the formed plasma axially to a certain extent. Experiments show that the novel discharge has directional preference depending on the applied voltage, a character of dielectric barrier discharge, and can run steadily for tens of hours without severe thermal load. Simulations using COMSOL Multiphysics reveal consistent variations of electron temperature and electron density with base pressure, input power, separation distance of isolated solenoids, and the number of turns of each solenoid. This ionization method is of great interest for plasma processing and propulsion in sub‐atmospheric environment.

Highly sensitive pressure and temperature induced SPP resonance shift at gold nanohole arrays.

Short range ordered (SRO) plasmonic nanohole arrays have a distinct surface plasmon polariton resonance in the visible region and exhibit an excellent sensing capability toward changes in the surrounding refractive index. While SRO and perfectly ordered plasmonic hole arrays have similar sensing properties, SRO arrays have clear advantages in fabrication, simplicity, and scalability. In this study, we use SRO gold nanoholes, which are subjected to pressure and temperature cycles, for vacuum and temperature sensing. The response of the transmission spectra to pressure changes in the range 10-3-105 Pa and temperature scans in the range 20-400 °C was recorded. Upon pressure cycling, a reversible response was observed. Upon initial temperature annealing, an irreversible blue shift in the resonance dip position was observed. Upon further temperature cycling, the resonance dip position shifts reversibly, with a notable red shift upon temperature increase. The results are discussed and interpreted based on possible molecular adsorption/desorption upon pressure cycling and in terms of the gold film's recrystallization, thermal expansion, and free electron density variations.

Rapid Variations in Electron Density Profiles in the Ionosphere Detected with the IZMIRAN High-Speed Ionosonde

The article presents a new technique for the measurement of rapid variations in electron density in the ionosphere based on the rapid obtainment of vertical sounding ionograms. The new technique uses broadband pulse signals, the spectrum of which can simultaneously cover the entire range of sounding frequencies. This leads to a reduction in the ionogram recording time. The technique has been implemented at the Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation (IZMIRAN) of the Russian Academy of Sciences in an experimental setup with the Bazis-M ionosonde and other industrial equipment. A significant reduction in the recording time of one ionogram has been achieved, down to ~2 s. A series of observations of rapid natural changes in the parameters of the ionosphere has been carried out on this experimental setup. Stratification of F1 and F2 layers of the ionosphere has been studied with the use of a numerical algorithm for solving the inverse sounding problem. It is shown that local disturbances of the electron density profile of ~5%, which can move downward at a speed of ~50 m/s, occur in a weakly disturbed, midlatitude ionosphere. It is also found that the electron density profiles can perform cyclic vertical motions with an amplitude of ~5 km and a period of ~90 s in the case of horizontal stratification.

Ionosphere over Ukrainian Antarctic Akademik Vernadsky station under minima of solar and magnetic activities, and daily insolation: case study for June 2019

We present ionospheric observational results obtained over Ukrainian Antarctic Akademik Vernadsky station. Ionospheric parameters (peak electron density and height, electron density and electron and ion temperatures in the topside) during the period near the local winter solstice in the Southern Hemisphere (June 28—29, 2019) are considered. The main objective is to show distinctive features of variations in ionospheric parameters during a prolonged period with very low solar and magnetic activities, and minimal daily insolation. Methods. F2 layer peak electron density and height were calculated from ionogramsobtained with ionosonde installed at the station with subsequent profile inversion. Defense Meteorological Satellite Program (DMSP) and Swarm data acquired over the station are used as well. Diurnal variations of electron density, and electron and ion temperatures at the altitude of the satellites’ orbits were calculated using a set of sub-models of the International Reference Ionosphere-2016 (IRI-2016) model. Results. We found a very good agreement between the observed and model variations of F2 layer peak electron density. Significant (by ~2 times) nighttime enhancement of electron density was observed on June 29. Electrondensity models show the similar increase of the density at the same time interval but this enhancement is much more smoothed comparing with the observations. Peak height values obtained using ionosonde are very close to ones calculated with the IRI-2016 sub-models. Satellite data are in a good consistency with the IRI model predictions, especially for electron density obtained by Swarm satellite. Conclusions. Multi-instrumental observations revealed a number of unique features of the ionosphere over Antarctic Peninsula under minima of solar and magnetic activities, and daily insolation.

Dependence of Detonation Velocity of Explosives on Effective Atomic Number and Effective Electron Density of the Explosives

Detonation velocity is one of the most important characteristics of explosives. For solid hydro carbon-based explosives it is generally greater than 4000 m/s. Detonation velocity depends to some extent upon the particle size of the explosives, increased charge diameter and increased confinement of the explosive. There is no report indicating the dependence of detonation velocity on the effective atomic number and effective electron density of the explosive. In the present work, we have arbitrarily chosen eight explosives. Four of these have detonation velocity between 9400 and 10100 m/s, and the other four has detonation velocity between 4500 and 5300 m/s. Direct method was used to calculate effective atomic number and effective electron densities various explosives. On calculating effective atomic number and effective electron density, it was found that detonation velocity of explosives does depend upon these two parameters. For explosives with high detonation velocity, effective atomic number is high and effective electron density is low while for low detonation velocity explosives it is reverse. It was also found that the variation of effective atomic number and effective electron density as a function of gamma ray energy can be explained on the basis of three different gamma ray inter action mechanism of gamma rays with matter.

Conjugate Observations of Dayside and Nightside VLF Chorus and QP Emissions Between Arase (ERG) and Kannuslehto, Finland

AbstractWe compare for the first time two conjugate events showing simultaneous very low frequency (VLF) wave observations between the same ground station and spacecraft, at different geomagnetic conditions and on opposite sides of the magnetosphere. Waves were observed at Kannuslehto (MLAT = 64.4°N, L=5.46), Finland, and on board Arase (Exploration of energization and Radiation in Geospace, ERG) in the inner magnetosphere. Case 1 on 28 March 2017 shows quasiperiodic (QP) emissions and chorus simultaneously observed on the postmidnight side during the recovery phase of a storm, with sustained high solar wind speed and AE index. Case 2 on 30 November 2017 shows clear one‐to‐one correspondence of QP elements on the noonside during geomagnetic quiet time (Dst>10 nT and AE<100 nT). We present the characteristics of both cases, focusing on coherence and spatial extent of the waves, electron density, and magnetic field variations. We report that the magnetic field gradient plays a role in the changes of spectral features of the waves.

Ionospheric induced plasma disturbances afore the m7.9 eastern Sichuan china earthquake of 12th may, 2008

A great number of earthquakes occur yearly in different areas and almost 100 -120 of them have a magnitude above 5. These seismic activities are very harmful for the inhabitants. Findings reveal that this seismo-electro-magnetic abnormality is a mirror image of some processes, which originated a few weeks before the main event and stay until few days after it. Plasma ion analyser (IAP) and Instrument Sonde de Langmuir (ISL) sensors) experiments available on Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) and Total Electron Content (TEC) from Global Positioning System (GPS) satellites, were employed to study the variations of electron and ion density for ionospheric disturbances before the M7.9 Eastern Sichuan China earthquake of 12th May, 2008. The study revealed seismo-ionospheric induced perturbations exactly three weeks afore the earthquake in all four investigated parameters. Electron density recorded 16.94 cm-3, electron temperature revealed - 2.25 o C while total ion density displayed 6.57 cm-1. The total electron content ranged from 4.28 to 3.6. The disturbance storm time (Dst) and planetary 3-hourly range (Kp) indices were used to classify pre-earthquake anomalies from the other anomalies associated with geomagnetic activities and was seen that this day (-21days relative to the earthquake) was devoid of geomagnetic storm, thus the observed perturbations were seismo-induced but not geomagnetic induced.

Low-frequency (ELF�VLF) radio atmospherics study at the Ukrainian Antarctic Akademik Vernadsky station

This paper describes the results of the atmospherics measurements in the extremely low-frequency (ELF) and very low-frequency (VLF) frequency ranges performed at the Akademik Vernadsky station (64.26W; 65.25S) during February–April 2019. The main objective of the study was the implementation of a single-site technique for monitoring the lower ionosphere parameters and locating globally distributed powerful lightning discharges. Methods. The receiving and analyzing VLF complex was used at the station to record two horizontal magnetic and vertical electric components of atmospherics in the frequency range 750 Hz – 24 kHz. A single-site lightning location method is based on the analysis of tweek-atmospherics (tweeks).It was implemented in the receiving system software. This allowed obtaining real-time information about lightning position, height and electron density variations in the lower ionosphere.The records of VLF atmospherics were synchronized via GPS timestamps with records of ELF transients resulted from globally distributed powerful lightning discharges. Results of analysis of tweeks recorded at the Akademik Vernadsky station indicates that lightning discharges are registered at distances from 2,000 km to about 10,000 km within the azimuthal sector, covering almost the entire South American continent, southern Africa and the Gulf of Guinea. Practically, no tweeks from the Pacific were recorded. This can be attributed to the non-reciprocity of attenuation of radio waves propagating in the west-east and east-west directions. In addition to the fundamental mode, we observed also the second and higher order modes of tweeks. This allowed estimating the lower boundary altitude and the electron density in the lower ionosphere. We demonstrated the advantages of simultaneous recordings of VLF atmospherics and ELF transients. Employing the vertical electric and two horizontal magnetic components measured by the VLF complex allowed for more accurate and unambiguous determining the source azimuth and resolving polarity of the charge transfer in the parent lightning discharges. Combining the ELF and VLF records, we can determine a distance to lightning and, then, parameters of the current moment of the lightning discharge. Conclusions. The performed experimental studies has shown the prospect of further combined ELF–VLF monitoring at the Akademik Vernadsky station, enabling detection of globally distributed powerful lightning discharges and changes in the lower ionosphere related to various phenomena of space weather, atmospheric and of terrestrial origin.

Characteristics of GNSS Total Electron Content Enhancements Over the Midlatitudes During a Geomagnetic Storm on 7 and 8 November 2004

AbstractThe characteristics of global electron density variations in the ionosphere during a geomagnetic storm on 7 and 8 November 2004 were investigated using total electron content (TEC) obtained from the global navigation satellite system (GNSS). The regions of enhanced TEC over North America, Europe, and Japan first appeared in the middle‐latitude regions. The TEC enhancements over North America showed a rapid longitudinal expansion and reached a wide longitudinal extent during the initial and main phases of the geomagnetic storm. TEC enhancements were simultaneously observed in both North America and Japan at 05:00 UT on 8 November. Observation data from the Defense Meteorological Satellite Program showed a slight enhancement of electron density at 850 km below the equatorward boundary of the middle‐latitude trough (45–48°N in geomagnetic latitude) over the Pacific Ocean. This electron density variation may correspond to the TEC enhancements observed in both Japan and North America. These results imply that an enhanced TEC region existed between North America and Japan. The TEC enhancement in Japan appeared with a magnetic conjugacy in the Southern Hemisphere, indicating one of the characteristics of storm‐enhanced density (SED). Moreover, TEC enhancements simultaneously appeared from Japan to central Asia at 11:00 UT on 8 November, corresponding to the early recovery phase of the geomagnetic storm. From the above results, it is suggested that SED phenomena can be simultaneously generated over a wide longitudinal width (~100°). The longitudinal extent of this SED event is 2.5–5.0 times longer than those reported by previous studies.

EFFECT OF VARYING VOLTAGE ON ELECTRON DENSITY IN OXYGEN HOMOGENEOUS DIELECTRIC BARRIER DISCHARGE UNDER ATMOSPHERIC PRESSURE

The formation of uniform dielectric barrier discharges (DBDs) under atmospheric pressure is a remarkable achievement with the addition of electronegative gasses in closed reactors. This work is the part of dielectric barrier discharge achieved under atmospheric pressure. A uniform glow discharge is produced in capacitive discharge reactor. An alternating voltage source (0-2.5) kV having frequency of 50Hz is applied across the two parallel disc electrodes. A couple of dielectrics (glass) used as a discharge barriers one on each electrode. The oxygen gas injected into the reactor controlled by mass flow controller with flow rate 30ml/min. The current-voltage waveforms for oxygen discharge achieved, fulfilling the basic conditions of discharge homogeneity. The diagnostic techniques rely on electrical discharge method and power balance method to differentiate discharges and estimate the electron density for different values of applied voltages. A significant relation is found indicating the variation of electron density with applied voltage.

Effect of the bond polarity on interlayer interactions in B–C–N layered materials: A dispersion-corrected density functional study

The interlayer interactions in nonpolar graphite and other BCN layered materials involving polar covalent bonds (h-BN, g-C3N4, graphite-like BC3 and BC2N) have been investigated by dispersion-corrected density functional calculations. Lattice parameters, bulk moduli and interlayer binding energies of these layered materials have been calculated using different dispersion correction schemes for comparison. Charge density difference plots have also been presented to elucidate the charge transfer behaviors along the nonpolar/polar covalent bonds as well as in the interlayer region. At first, graphite and h-BN were examined as benchmarks; the former contains planar graphene layers regardless of the interlayer binding, while the monolayers in the latter exhibit an asymmetric charge distribution along the BN polar bonds, leading to a slightly puckered feature induced by the interlayer interaction. Similar geometric deviations have also been observed in other layered structures involving CN and/or BC polar bonds, but with distinct characteristics directly related to their specific interlayer stacking situations. By contrast, all of the isolated monolayers free from interlayer binding show a pristine planar feature in despite of the polar covalent bonds involved. Our theoretical findings further address the necessity of considering the electron-density variations induced by specific bonding environments in polar BCN layered materials, which can be properly described by the Tkatchenko-Scheffler correction.

Blue phosphorene nanoribbon for detection of chloroform vapours – a first-principles study

ABSTRACT Using density functional theory (DFT) technique, we explored the interaction behaviour of target chloroform (CHCl3) molecules on armchair blue phosphorene nanoribbon (ABPNR). Besides, van-der-Waals dispersion correction (vdW-DF) density functional is included in the adsorption studies for accurate calculation. The most preferential adsorption sites (ring, bridge, and top site) of CHCl3 on ABPNR were considered in the study. Initially, the structural stability of ABPNR system is confirmed with the negative magnitude of formation energy – 4.82 eV. The energy gap of pristine ABPNR is calculated to be 1.78 eV. The semiconductor nature of ABPNR facilitates it to be used as chemical sensor. The transfer of charge takes place between ABPNR and CHCl3 that leads to variation in energy gap and electron density upon adsorption of CHCl3 molecules. Thus, the report suggests the use of ABPNR as an efficient sensing substrate for CHCl3 vapours.

Multichannel filter application of a magnetized cold plasma defect in periodic structure of ZnS/TiO2 materials

In this article, transmission spectra of multilayer structure of zinc sulfide (ZnS) and titanium dioxide (TiO2) with defect of magnetized cold plasma (MCP) have been calculated theoretically by using characteristics transfer matrix method. The transmission spectra versus frequency have been analyzed for symmetric and asymmetric structure. Due to have a multiple band gaps in the asymmetric structure, we have taken the asymmetric structure for analysis with the parameters of MCP and the thicknesses of the dielectric materials. It is well known that magnetized cold plasma is an abnormal material because the permittivity changes with applied external magnetic field, and shows tunable photonic band gap for permittivity of the MCP. Now, the transmission spectra of the asymmetric structure versus frequency by inserting one or two magnetized cold plasma layer were analyzed with the variation of incident angles, the parameters of MCP, and the thicknesses of ZnS and TiO2 material. The analyzed transmission spectra of asymmetric structure with the variation of electron density, thicknesses of dielectric materials were obtained better results with defect of two plasma layers as compare to the defect of one layer of plasma. These obtained results reveal that the defect of two magnetized cold plasma layers of one dimensional asymmetric structure of ZnS, TiO2 may be used for the tunable multichannel filter at microwave region.

Boron trifluoride interaction studies on graphdiyne nanotubes – A first-principles insight

We investigated the adsorption of boron trifluoride (BF3) gas molecules on graphdiyne nanotube (G2YNT) based on first-principles studies. We ensured the stability of G2YNT using cohesive energy and found stable. G2YNT shows semiconductor properties. Thus, it is used as the base material to adsorb BF3 gas molecules. The band structure modification and changes in the electron density is noticed via the projected density of states (PDOS) spectrum. Also, the electron density variation in G2YNT reveals the adsorption of BF3 molecules. The results of the work suggest that G2YNT is a promising material to perceive the existence of toxic BF3 molecules.

Ultrafast Structural Changes Decomposed from Serial Crystallographic Data.

Direct visualization of electronic and molecular events during biochemical reactions is essential to mechanistic insights. This Letter presents an in-depth analysis of the serial crystallographic data sets collected by Barends and Schlichting et al. ( Science 2015 , 350 , 445 ) that probe the ligand photodissociation in carbonmonoxy myoglobin. This analysis reveals electron density changes caused by the formation of high-spin 3d atomic orbitals of the heme iron upon photolysis and their dynamic behaviors within the first few picoseconds. The heme iron is found popping out of and recoiling back into the heme plane in succession. These findings provide long-awaited visual validations for previous works using ultrafast spectroscopy and molecular dynamics simulations. Electron density variations are also found largely in the solvent during the first period of a low-frequency oscillation. This work demonstrates the importance of the analytical methods in detecting and isolating weak, transient signals of electronic changes arising from chemical reactions.

Comparison of Ground‐Based Ionospheric Scintillation Observations With In Situ Electron Density Variations as Measured by the Swarm Satellites

AbstractIonospheric scintillation is known to be associated with irregularities in electron density, which manifests as rapid fluctuations in the amplitude and phase of radio signals traversing the ionosphere. The scintillations caused by irregularity structures in the ionosphere can be directly measured using ground‐based GPS scintillation measurement receivers. In this work we have used in situ measurements of electron density by means of the Langmuir probe on the Swarm satellites to derive an index called the rate of density index (RODI). Using a ground‐based International Global Navigation Satellite Systems Service receivers and one dedicated scintillation measurement receiver, we have examined if we can identify ionospheric scintillation events that are correlated with space‐based electron density variations characterized by the RODI for cases when the Swarm satellites orbital tracks traverse coincidental locations to the ground‐based station. The selected Swarm B passes over Africa have been limited to the longitudes within ±7° of longitude relative to the position of a dedicated scintillation receiver located at Pwani, Kenya (Geo. Lon: 39.78°E, Geo. Lat: 3.24°S). Our results show that RODI could be a useful index for detecting irregularities associated with scintillation events that can also be observed from the ground. There is a similarity in RODI fluctuations and ground‐based irregularity measures based on rate of total electron content index with an asymmetry in irregularity activity across African region. There is stronger irregularity activity and high background nighttimes electron density on the western side of Africa than on the eastern side. This work shows the potential of using space‐based in situ measurement for scintillation detection and mitigation for operational purposes particularly for regions where terrestrial scintillation measurement are not possible like over oceans and deserts.

VLF Measurements and Modeling of the D-Region Response to the 2017 Total Solar Eclipse

In this paper, we report measurements in Colorado and Utah of the disturbed very-low-frequency (VLF) signals from the NML Navy transmitter in North Dakota during the 2017 solar eclipse. Using an occultation mask of solar fluxes together with detailed chemistry and VLF propagation simulations, we quantify the D-region response to the eclipse, in terms of electron density variation, as well as the expected signatures of VLF transmitter signals. The VLF measurements, including an anomalous amplitude enhancement recorded in UT, can be quantitatively explained using the Wait and Spies ionospheric profile with a sharpness parameter of $\beta = 0.3$ km−1 above ~55 km and an increase in the D-region ionosphere height of $\Delta h' \simeq 8$ km. This sharpness parameter is consistent with previously reported rocket measurements and first-principles calculations. The best-fit results suggest a reduction of D-region electron density by ~90% during the eclipse in the D-region, implying an occultation of Lyman- $\alpha $ by nearly 99%. This finding agrees with detailed calculations of time-dependent obscuration factors utilizing the He 30.4-nm images from Solar Dynamics Observatory as a proxy for the distribution of Lyman- $\alpha $ across the solar disk and limb. Moreover, the present results show that subionospheric VLF propagation is sensitive to the sharpness parameter of the electron density profile in the D-region. Previously reported first-principles simulations have shown that the sharpness parameter is mostly controlled by the background concentration of minor neutral species. Thus, the VLF technique can be likely used to remotely sense these neutral species at and below the effective reflection altitudes of VLF waves.

Exploring the detailed spectroscopic characteristics, chemical and biological activity of two cyanopyrazine-2-carboxamide derivatives using experimental and theoretical tools.

This article represents the spectroscopic and computational studies of two new pyrazine compounds. In order to establish the structure and functional nature of the compounds, we have employed Fourier transformed infrared (FT-IR) and Raman spectra, nuclear magnetic resonance (NMR) spectra, and ultraviolet (UV) absorptions and have compared them with the simulated computational spectra and found that they are in the agreeable range. Simulated hyperpolarisability values are used to obtain the nonlinear optic (NLO) activity of the compound, to be used in organic electronic materials. The charge transfer and related properties was investigated by the simulation of electronic spectrum with time dependent density functional theory (TD-DFT). Natural transition orbitals (NTO) provides information about which region of the molecules are more involved in the electronic transitions and the charge transfer properties for the lowest energy excitation have been analyzed on the basis of electron density variation. Molecular dynamics simulations provide information about the behavior of the molecule in solutions. Frontier orbital analysis and study of various reactivity descriptors like ALIE and Fukui provided deep knowledge on the reactivity side. Molecular docking has been also performed to investigate the interaction between title molecules and exhibits inhibitory activity against Pseudomonas aeruginosa Enoyl-Acyl carrier protein reductase (Fabl).

Study of laser-induced-plasma parameters for molybdenum targets

Molybdenum targets were irradiated with 2-ns 300-mJ pulses from an Nd:YAG laser at its second harmonic wavelength of 532 nm at a repetition rate of 10 Hz in open air. The radiation emitted from laser-induced plasma from the Mo target in the Local Thermal Equilibrium (LTE) state was analyzed. The temperature of the plasma was calculated using a Boltzmann-plot method. The electron density was determined from the Stark broadening via the comparison of the electron densities of different neutral molybdenum lines (465.5, 498, 517 and 550 nm) with hydrogen Hα-line (656.3 nm). We studied the variation of electron density and electron temperature as a function of μs-delay times and laser fluencies at different distances from the target surface. It was found that the neutral molybdenum lines suffer from self-absorption. The self-absorption changes the values of the electron density and the electron temperature due to the decrease in the line intensity and the increase in the line width and hence leads to the distortion in the line shape. The Mo I lines were corrected against self-absorption and the corrected values of the temperature and the electron density were obtained.