Model Of Electron Density Profile Research Articles

Construction and Application of Global Middle- and Low-Latitude Bottomside Electron Density Profile Model Based on Multisource Satellite Geodetic Data and International Reference Ionosphere Model

Construction and Application of Global Middle- and Low-Latitude Bottomside Electron Density Profile Model Based on Multisource Satellite Geodetic Data and International Reference Ionosphere Model

A Global Empirical Model of Electron Density Profile in the F Region Ionosphere Basing on COSMIC Measurements

AbstractThe topside ionosphere accounts for a dominant part of the ionospheric total electron content, whereas accurate global modeling of topside ionospheric electron density (Ne) profile has not been fully achieved. In this study, a high precision Ne profile model, named α‐Chapman Based Electron Density Profile Model (α‐Chapman‐Based‐EDP), was built by using ∼4.5 million Ne profiles from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC‐1) radio occultations. We first describe each of the profiles using five parameters of the α‐Chapman function, that is, peak density (NmF2) and height (hmF2) of F2 layer, scale height (Hm) as well as its altitude change rates, and then built a model for each of the parameters as a function of latitude, longitude, month, local time, and solar activity, through Empirical orthogonal function (EOF) analysis and Fourier expansion. Combining all the five models, we construct the α‐Chapman‐Based‐EDP. Compared with observations from COSMIC‐1 and ‐2, the model captures the ionospheric climatology well, such as solar activity dependence, seasonal variation, and spatial pattern, including the equatorial ionization anomaly and midlatitude trough as well as their variabilities. Our model can describe nearly 80% variability of Ne in F region. In contrast, the IRI2016 cannot well reproduce these characteristics, with errors higher than our model. The potential applications of our model were also discussed. A dense matrix data calculated by the model will be released in https://www.researchgate.net/profile/Qiaoling_Li5 with the permissions of COSMIC organizations.

A Variable Nano Capacitor Behaved Arising from Lipid Bilayers of DMPC

Bio-membranes are thin capacitors and because the membrane has a dynamic behavior and in the various positions has different area and thickness, the capacitance of the membrane is not fixed and causes a variable capacitor. In this study, we have shown the model of a microscale dielectric membrane capacitor including DMPC structures. We have shown that Quantum effect has appeared in a small free space of the membrane thickness due to number of phospholipids layers. In addition, we have specifically investigated the quantum and coulomb blocked effects of different thickness. Furthermore, the electron density profile models, electron localization function (ELF) and local information entropy have been applied as a formal way to studies the interaction of protein with lipid bilayers in cell membrane.

THE ELECTRON DENSITY PROFILE INVERSION FOR INCOMPLETELY DEVELOPED CASE OF F1 LAYER

AbstractThe electron density profile inversion from vertical incidence ionograms is essential for research in ionospheric structures and movements, wave propagation and space weather applications, hence has gathered very wide attention. The echo trace of incompletely developed F1 layer is common in vertical incidence ionograms, and it is usually expressed as smooth transition from F1 layer to F2 layer, not a cusp appeared at the critical frequency of F1 layer. However, the existing ionospheric models and inversion algorithms are generally intended for the completely developed F1 layer with the assumptions of a parabolic profile and an infinite slope at the peak of F1 layer, which are not suitable for the profile of incompletely developed F1 layer which achieves the maximum electron density of F1 layer and enters F2 layer at the peak of F1 layer and has a finite slope. Consequently, an F1 layer electron density profile model based on the shifted Chebyshev polynomial for incompletely developed case of F1 layer is introduced with a parameter named as the model setting critical frequency. Taking into account the profile smoothness, an electron density profile inversion algorithm with constrained optimization F1 and F2 layer parameters based on the model mentioned above is proposed. The validity of the model and the inversion algorithm is analyzed through the simulation, and the effectivity of the proposed algorithm is further verified by the comparison between the synthesized vertical sounding & oblique sounding traces and the measured data.

Cell membrane causes the lipid bilayers to behave as variable capacitors: A resonance with self-induction of helical proteins

Cell membrane has a unique feature of storing biological energies in a physiologically relevant environment. This study illustrates a capacitor model of biological cell membrane including DPPC structures. The electron density profile models, electron localization function (ELF) and local information entropy have been applied to study the interaction of proteins with lipid bilayers in the cell membrane. The quantum and coulomb blockade effects of different thicknesses in the membrane have also been specifically investigated. It has been exhibited the quantum effects can appear in a small region of the free space within the membrane thickness due to the number and type of phospholipid layers. In addition, from the viewpoint of quantum effects by Heisenberg rule, it is shown the quantum tunneling is allowed in some micro positions while it is forbidden in other forms of membrane capacitor systems. Due to the dynamical behavior of the cell membrane, its capacitance is not fixed which results a variable capacitor. In presence of the external fields through protein trance membrane or ions, charges exert forces that can influence the state of the cell membrane. This causes to appear the charge capacitive susceptibility that can resonate with self-induction of helical coils; the resonance of which is the main reason for various biological pulses.

SWAXS investigations on diffuse boundary nanostructures of metallic nanoparticles synthesized by electrical discharges

Metallic nanoparticles have attracted a particular interest in scientific research and industrial applications due to their unique size-dependent physical and chemical properties. An eco-friendly and cost-effective synthesis method called electrical discharge enables large scale production of metallic nanoparticles. Systematic investigations of such synthesized metallic nanoparticles help to optimize the synthesis process and improve the product quality. In this work, for the first time we have investigated the diffuse interfacial boundary nanostructures of the metallic nanoparticles, which were synthesized under different conditions by electrical glow and arc discharges in the carrier gas, by means of a small- and wide-angle X-ray scattering (SWAXS) technique using a laboratory X-ray source. Meanwhile, this unique SWAXS technique allows simultaneous study of the primary particle size, morphology, and crystallinity. The metallic nanoparticles (copper and nickel) under investigation cover a size range of 10–80 nm, and the determined thickness of the diffuse boundary nanostructured layer of metallic nanoparticles is in the range of 1–3 nm. The experimental results obtained by SWAXS were compared to the TEM/EDX observation and the XRD reference patterns from RRUFF database, and a good agreement was found. Our SWAXS investigations indicated that the existence of a diffuse nanostructured solid layer on the synthesized metallic nanoparticle surface causes a negative deviation of the scattering intensity \(\left( {I \propto q^{ - \alpha } ,\;\alpha > 4} \right)\) from Porod’s law which corresponds to the case of ideal two-phase particle systems with sharp boundaries \(\left( {I \propto q^{ - \alpha } ,\;\alpha = 4} \right)\). This implies that the electron density profile is not sharp but changes gradually between two phases, and hence the exponent α is greater than four. Two electron density profile models, sigmoidal electron-density gradient model and linear electron-density gradient model, have been taken into account in determining the thickness of the diffuse boundary nanostructured layer. Combined with the SWAXS experimental results, the possible mechanisms of the formation of the diffuse boundary nanostructured layer of the metallic nanoparticles synthesized by electrical glow and arc discharges in the gas phase have been discussed in detail.

A Time-Dependent Collisional Sheath Model for Dual-Frequency Capacitively Coupled RF Plasma

A time-dependent analytical model for capacitive sheath is developed for describing collisional radio-frequency sheath driven by two sinusoidal sources. In this model, it has been assumed that ion motion and velocity are time varying and sheath is collisional. The time-dependent terms in ion-fluid equations are ignored. Based on the assumption of steplike electron density profile model, analytical expressions for instantaneous sheath motion and sheath potential have been developed. The plasma-sheath motion and sheath potential are compared with a time-dependent model for collisionless and a time-independent model for collisional capacitively coupled plasma.

Estimation of probability of occurrence of F1 layer or L condition using tables and electron density profile models

An algorithm is proposed for evaluation of the probability of occurrence of an F1 layer or L condition, based on tables. Observations independent of the tables database are used for comparison between the estimated probability of occurrence, the formulation used at present in IRI, and the occurrence actually observed. The importance of the inclusion of L condition in the electron density profile model is shown.

Electron density profile calculation technique for Autoscala ionogram analysis

An electron density profile model with free parameters is introduced. Initially the parameters are calculated on the basis of the ionospheric characteristics automatically obtained from the ionograms by Autoscala and considering the helio-geophysical conditions. The technique used to adjust the free parameters to the particular ionograms recorded is presented.

Diurnal and seasonal variation of the ionogram-derived scale height at the F2 peak

The Chapman scale height H T at F2 peak, which can be used to construct a topside electron density profile model, is deduced from ground-based ionograms. In this paper, H T values obtained from ionograms recorded at the low latitude station Hainan (19.4°N, 109.0°E), China is used to study its diurnal, seasonal, and solar activity dependence. The correlations between H T and the F2 peak parameters foF2 and hmF2, the best-fitted IRI-parameter B0, and the ionospheric slab thickness τ are also studied. Data used for the present study covered a 2-year time period from March 2002 to February 2004. The present study showed that: (1) Diurnal course of the H T has two peaks, with the main one occurring at daytime hours around noontime and the other occurring before sunrise. The pre-sunrise peak is most obvious for winter compared with that for summer and equinox. The minimum values of H T occur around midnight and sunrise hours. The time of occurrence of the sunrise minimum is earliest for summer and latest for winter. (2) H T shows a clear annual variation with largest daytime values occurring in summer and smallest values in winter. (3) H T shows strong solar activity dependence, with the daytime value of H T decreasing with decreasing solar activity. (4) H T is strongly correlated with the bottomside F2 layer thickness parameter B0 and the ionospheric slab thickness τ. The high correlation between H T and B0 parameter suggests the possibility to construct the topside electron density profile model based on the B0 parameter previously established for the International Reference Ionosphere.

Electron density height profiles from GPS receiver data

A successful ionospheric electron density model assimilates relevant data for determination of its driving parameters. We process about two hours worth of two‐frequency GPS ground‐receiver data from five satellites in order to separate the least squares solution of up to four driving parameters of the electron density profile (EDP) model from the solution of four relative (between satellites) differential hardware biases. The EDP model we use is part of the Ionosphere and Troposphere Raytrace Model (ITRAY), which is our upgrade of the Raytrace/Ionospheric Conductivity and Electron Density model (ICED)‐Bent‐Gallagher (RIBG) model. We use the Westford GPS receiver in Massachusetts to update the EDP model, which we then use to predict EDP distributions at nearby Millstone Hill for comparison with ground truth incoherent‐scatter radar and Digisonde data. We find that a simple procedure often works well when the model time dependence is correct, but we find that forcing the ionospheric model to more closely fit GPS data actually degrades ionospheric specification in the F layer region. We suggest a data diversification remedy.

X-ray reflectivity and AFM studies of polystyrene-CdS nanocomposite thin films

Nanocrystalline CdS particles have been synthesized and dispersed in a polystyrene (PS) medium in the form of thin composite films. X-ray reflectivity and atomic force microscopy (AFM) have been used to study the films. CdS particles are found to precipitate towards the bottom of the films giving rise to a continuous change in the electron density along the depth of the film. It is shown that previous knowledge about the realistic model of electron density profile is required for correct interpretation of the X-ray reflectivity data for systems where electron density changes continuously and independent information obtained from atomic force microscopic studies can be used conveniently for this purpose.

Performance prediction methods of HF radio systems

A survey of the historical development of methods for predicting the performance of ionospheric HF radio systems is presented, with special emphasis on modelling. The models considered are ionospheric characteristics and electron-density profile models, a propagation model, transmission loss and gain factors models, characteristics of radio noise models and a reliability model.

Matrix element and transition rate for Auger neutralization of low energy ions near metal surfaces

A model for direct Auger neutralization of low energy ions near metal surfaces is outlined, and used to calculate the dependence of the transition rates for the H(ls)-Au and H(ls)-Al interactions on ion-surface separation. A one-parameter variational atomic state wavefunction is used in the calculation of the transition amplitude. The corresponding transition rate contains significant contributions from metallic electrons with a wide range of momenta, and a major contribution from transitions in which the Auger electron does not escape from the metal. The absolute transition rate is a sensitive function of the surface electron density profile model, but can be well represented, over a wide range of ion-surface separations S, by the simple exponential form A e − aS , where A and a are constants.

Matrix element and transition rate for Auger neutralization of low energy ions near metal surfaces

Abstract A model for direct Auger neutralization of low energy ions near metal surfaces is outlined, and used to calculate the dependence of the transition rates for the H(ls)-Au and H(ls)-Al interactions on ion-surface separation. A one-parameter variational atomic state wavefunction is used in the calculation of the transition amplitude. The corresponding transition rate contains significant contributions from metallic electrons with a wide range of momenta, and a major contribution from transitions in which the Auger electron does not escape from the metal. The absolute transition rate is a sensitive function of the surface electron density profile model, but can be well represented, over a wide range of ion-surface separations S, by the simple exponential form A e−aS, where A and a are constants.

A note on the electron density profile at the surface of metals

A two step model of electron density profile at the surface of a metal is in use for the study of surface plasmas. The same model is used here to calculate surface energy and work function. The parameters in the model are determined by minimizing surface energy. It is shown that the model is a reasonable approximation to the true profile only in low density metals.

A note on the electron density profile at the surface of metals

A two step model of electron density profile at the surface of a metal is in use for the study of surface plasmas. The same model is used here to calculate surface energy and work function. The parameters in the model are determined by minimizing surface energy. It is shown that the model is a reasonable approximation to the true profile only in low density metals.

D-region processes at equatorial latitudes

Our current understanding of the ionization production and loss processes, and electron and ion density distributions in the undisturbed D-region are reviewed with special reference to the equatorial latitudes. The importance of combining ground-based measurements with rocket-borne measurements in the development of D-region electron density profile models is stressed. The need for coordinated experiments at low latitudes for investigating outstanding problems related to the quiet D-region is emphasized.