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Yen-hsyang Chu - One of the best experts on this subject based on the ideXlab platform.
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reply to comment by lei et al on a new aspect of ionospheric e region Electron Density morphology
Journal of Geophysical Research, 2010Co-Authors: Yen-hsyang ChuAbstract:[1] Since the FORMOSAT‐3/COSMIC satellites were launched in April 2006, ionospheric Electron Density profiles have been retrieved from the excess phase of the GPS signal by using the radio occultation technique and can be accessed from the Web site http://www.cosmic.ucar.edu/. On the basis of these Electron Density profiles and the use of data quality control criteria developed by Yang et al. [2009], Chu et al. [2009] investigated E region Electron Density morphology and showed that the general properties of the COSMIC‐ retrieved E region Electron Density are in good agreement with the predictions of the Chapman layer theory that was developed in accordance with photochemical process and controlled by solar zenith angle. Nevertheless, Chu et al. [2009] found existences of salient enhancements in the noontime E region Electron Density not only at the geomagnetic equator but also in the geomagnetic latitude regions ±15°−35°, which cannot be explained by the Chapman layer theory. In addition, they also provided compelling evidence to show the presence of longitudinal wave number 3 and 4 structures of the equatorial Electron Density in a height range of 100–200 km, which is in excellent agreement with longitudinal structures of equatorial electrojet intensity derived from equatorial magnetic field data obtained by the Orsted, CHAMP, and SAC‐C satellites during the years 1999–2006. [2] On the basis of the simulation result obtained by Yue et al. [2010], Lei et al. [2010] question the validity of the E region Electron Density retrieved by the GPS radio occultation technique. They argue that because of the presence of the ionospheric Electron Density gradient in the horizontal direction that violates the spherical symmetry assumption of the Abel transform for inverting ionospheric Electron Density profile from calibrated total Electron content along the GPS raypath, the COSMIC‐measured E region Electron Density enhancements in midlatitude regions were caused by the retrieval error of the GPS radio occultation process. From Figure 1 of Lei et al. [2010] (identical to Figure 2 of Yue et al. [2010]), the simulation‐retrieved E region Electron densities around 100 km in equinox season are approximately 50– 100% and 150–200% greater than the “true” model values at the geomagnetic equator and in geomagnetic latitude regions ±30°−50°, respectively. In addition, the former are about 150–200% smaller than the latter in geomagnetic latitude regions ±10°−30°. If the simulation‐retrieved results obtained by Yue et al. [2010] were true and able to be representative of the general GPS occultation‐retrieved results, the morphologies of the COSMIC‐measured E region Electron Density should be in accord with those of the simulation results. Namely, the E region Electron Density retrieved by COSMIC satellites should be much greater (smaller) than true measurement made by the ground‐based ionosonde in geomagnetic latitude regions ±30°–50° (±10°–30°). In order to validate the simulation‐retrieved results, we compare peak values of E layer Electron Density NmE between COSMIC retrieval and global ionosonde measurement in the different latitudinal regions for July 2006 to July 2009. The COSMIC data were selected for comparison if the separation between COSMIC occultation point and ionosonde station is 10 min in time and 2.5° in space. Figure 1 presents an example of latitudinal variation in histograms of percent errors of NmE between COSMIC retrieval and ionosonde measurement for spring (March–May) 2007–2009, in which the percent error (PE) is defined by
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A new aspect of ionospheric E region Electron Density morphology
Journal of Geophysical Research: Space Physics, 2009Co-Authors: Yen-hsyang ChuAbstract:[1] From global measurements of ionospheric Electron Density profiles made by the FORMOSAT-3/COSMIC satellites, the morphology of E region Electron Density is investigated. Seasonal, latitudinal, and diurnal variations in daytime E region Electron Density are well described by the Chapman theory, and the E layer peak Electron Density NmE and its peak height hmE are governed by the solar zenith angle χ in accordance with relations NmE ∝(cosχ)p and hmE ∝ln(secχ), respectively. However, it is revealed that there are three geomagnetic latitude regions where striking enhancements of the E region Electron Density occur. One of them is located at the geomagnetic equator with relatively narrow latitude extent of about 6°–10°, and the other two with much wider latitude extent of about 10°–20° appear on both sides of the geomagnetic equator in latitude regions ±20°–30°, respectively. The locations of these E region Density enhancements are asymmetrical about the geomagnetic equator in solstice seasons, and they have a salient tendency to shift toward (away from) the summer (winter) hemisphere. The off-equator E region Electron Density enhancements are closely connected with the bottomside of the F region equatorial anomaly crests, where the component of the Electron Density parallel to the magnetic field line is maximum. It appears that the off-equator E region Electron Density enhancements are very likely the footprints of the F region equatorial anomaly crests. The morphologies of the exponent n and coefficient K in the power law relation between χ and foE (E region critical frequency) are also examined. There is a tendency for the n and K values to be larger in local winter than in local summer seasons in the latitudinal regions the same as the off-equator Electron Density enhancements. In addition, it is found that a minor peak in the K values is nearly continuously present in all seasons over the geomagnetic equator. A comparison shows significant discrepancies in the E region Electron Density morphologies between COSMIC measurement and IRI model prediction. Furthermore, compelling evidence is provided to show the presences of longitudinal wave number 3 and 4 structures of the Electron Density in the height region 100–200 km, which are in coincident with the longitudinal structures of equatorial electrojet. It is believed that these longitudinal 3- and 4-peak structures are very likely associated with nonmigrating diurnal tides propagating eastward in ionospheric E region.
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an examination of formosat 3 cosmic ionospheric Electron Density profile data quality criteria and comparisons with the iri model
Terrestrial Atmospheric and Oceanic Sciences, 2009Co-Authors: Kuofeng Yang, Yen-hsyang Chu, Chienya WangAbstract:In this article, we analyze the properties of ionospheric Electron Density profiling retrieved from FORMOSAT-3/COSMIC radio occultation measurements. Two parameters, namely, the gradient and fluctuation of the topside Electron Density profile, serve as indicators to quantitatively describe the data quality of the retrieved Electron Density profile. On the basis of 8 month data (June 2006-January 2007), we find that on average 93% of the Electron Density profiles have upper Electron Density gradients and Electron Density fluctuations smaller than -0.02 #/m^3/m and 0.2, respectively, which can be treated as good data for further analysis. The same results are also achieved for the peak height of the Electron Density. After removing the questionable data, we compare the general behaviors of the Electron Density between FORMOSAT-3 and the IRI model. It is found that the global distributions of the peak height and the peak Electron Density for the FORMOSAT-3/COSMIC data are generally consistent with those for the IRI model. However, a significant difference between their scale heights of the topside Electron Density profiles is found. It suggests that the shape of the topside Electron Density profile in the IRI model should be revised accordingly such that it more closely resembles the real situation.
Alan A Pinkerton - One of the best experts on this subject based on the ideXlab platform.
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chemical bonding in cesium uranyl chloride based on the experimental Electron Density distribution
Inorganic Chemistry, 2011Co-Authors: Vladimir V. Zhurov, Elizabeth A. Zhurova, Alan A PinkertonAbstract:Details of the Electron Density distribution in Cs(2)UO(2)Cl(4) have been obtained from an accurate X-ray diffraction experiment at 20 K. The Electron Density was described with the Hansen-Coppens multipole model. Topological analysis of the Electron Density confirms that the U-O bond is probably a triple bond, the U-Cl bonds are incipient covalent interactions, and the Cs-Cl and Cs-O interactions are of the closed-shell type. The results obtained serve as a proof of principle that Electron Density features related to chemical bonding may be obtained from X-ray data for even the heaviest elements.
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experimental Electron Density studies of non steroidal synthetic estrogens diethylstilbestrol and dienestrol
Journal of Molecular Structure, 2008Co-Authors: Eric J Yearley, Elizabeth A. Zhurova, Vladimir V. Zhurov, Alan A PinkertonAbstract:Abstract An experimental charge Density analysis has been carried out on two synthetic estrogens, diethylstilbestrol (DES) and dienestrol (DNS), to further investigate the alignment and binding of estrogenic compounds to the estrogen receptor, and to also establish a relationship between the biological function and the Electronic properties of steroidal and non-steroidal estrogens by analysis of their Electron Density distribution. X-ray diffraction data for DES and DNS were obtained using a Rigaku R -Axis Rapid high-power rotating anode diffractometer with a curved image plate detector at 20(1) K. The total Electron Density was modeled using the Hansen–Coppens multipole model. Relatively strong O···H O hydrogen bonds, weak O···H C hydrogen bonds, and a number of intermolecular H···H interactions were characterized from the topological analyses of the total Electron Density of DES and DNS. Mapping of the electrostatic potential onto the molecular surface revealed negative regions around all the hydroxyl oxygens, above and below the aromatic rings as expected from previous studies. A proposed alignment and binding of DES and DNS to the estrogen receptor is discussed in terms of the atomic charges and electrostatic potential derived from the Electron Density distribution.
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experimental and theoretical Electron Density study of estrone
Journal of the American Chemical Society, 2006Co-Authors: Elizabeth A. Zhurova, Vladimir V. Zhurov, Cherif F Matta, Alan A PinkertonAbstract:The Electron Density and the electrostatic potential (ESP) distributions of estrone have been determined using X-ray diffraction analysis and compared with theoretical calculations in the solid and gas phases. X-ray diffraction measurements are performed with a Rigaku Rapid rotating anode diffractometer at 20 K. The Electron Density in the estrone crystal has been described with the multipole model, which allowed extensive topological analysis and calculation of the ESP. From DFT calculations in the solid state a theoretical X-ray diffraction data set has been produced and treated in the same way as the experimental data. Two sets of single molecule DFT calculations were performed: (a) An Electron Density distribution was obtained via a single-point calculation with a large basis set at the experimental geometry and subsequently analyzed according to the quantum theory of atoms in molecules (AIM) to obtain the bond and most atomic properties, and (b) another Electron Density distribution was obtained wit...
Xinan Yue - One of the best experts on this subject based on the ideXlab platform.
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global ionospheric Electron Density estimation based on multisource tec data assimilation
Gps Solutions, 2017Co-Authors: Chengli She, Weixing Wan, Xinan Yue, Bo Xiong, Feng Ding, Biqiang ZhaoAbstract:We developed a parameterized ionospheric Electron Density model based on the IRI-2012 model by spherical harmonic expansions in the horizontal and empirical orthogonal functions in the vertical. Then, after assimilating the monthly multisource total Electron content (TEC) data from ground-based GPS, LEO radio occultation (RO), and the oceanic altimeter during magnetically quiet time into the model, we reanalyzed the monthly global ionospheric Electron Density TEC and other key parameters such as foF2 and NmF2. Both the reanalyzed and IRI-2012 model results were compared to the TEC measurements, the monthly median foF2 in a middle-latitude ionosonde station, and the global TEC map from CODE. The comparisons showed that both the reanalyzed and IRI results are consistent with those observations and the reanalyzed results perform better than the IRI model. Furthermore, the reanalyzed results are also consistent with the retrieved maps of HmF2, NmF2, and TEC from COSMIC RO observations. In summary, our method can reanalyze the global TEC and Electron Density using multisource TEC data assimilated into our model and improve the performance of IRI model.
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Longitudinal variations of the nighttime E layer Electron Density in the auroral zone
Journal of Geophysical Research: Space Physics, 2015Co-Authors: Xiaoli Luan, Wenbin Wang, Xiankang Dou, Alan Burns, Xinan YueAbstract:Longitudinal variations of the nighttime E layer Electron Density (21:00–03:00 magnetic local time) in the auroral zone are investigated, and their sources are discussed in terms of auroral precipitation and solar radiation. The Electron Density data used in this study are retrieved from Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation observations during 2006–2009 under quiet geomagnetic activity (Kp ≤ 3) and solar minimum conditions. The main conclusions of this study are as follows: (1) the nighttime E layer Electron Density had pronounced longitudinal variations in the auroral zone. These variations depended on season and had large hemispheric asymmetry for all seasons. In winter, relatively larger Electron Density was located in 120–310° magnetic longitude (MLON) in the northern hemisphere and in 170–360° MLON in the southern hemisphere, and greater maximum Density occurred in the northern hemisphere than in the southern one. In summer and equinox, the longitudinal asymmetry was greater in the southern hemisphere. (2) The peaks of the E layer Electron Density along latitude generally occurred between 65° and 70° magnetic latitude in the auroral zone in all seasons for both hemispheres except for the sunlit sector of the southern summer. (3) The greater Electron Density in local winter in the auroral zone was generally associated with the more intense auroral precipitation intensity at roughly the same longitude, whereas the longitudinal patterns of the Electron Density were under the combined impact of both auroral precipitation and solar radiation in the local summer and equinoxes.
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error analysis of abel retrieved Electron Density profiles from radio occultation measurements
Annales Geophysicae, 2010Co-Authors: Xinan Yue, William Schreiner, Jiuhou Lei, Sergey Sokolovskiy, C Rocken, Douglas Hunt, Yinghwa KuoAbstract:Abstract. This letter reports for the first time the simulated error distribution of radio occultation (RO) Electron Density profiles (EDPs) from the Abel inversion in a systematic way. Occultation events observed by the COSMIC satellites are simulated during the spring equinox of 2008 by calculating the integrated total Electron content (TEC) along the COSMIC occultation paths with the "true" Electron Density from an empirical model. The retrieval errors are computed by comparing the retrieved EDPs with the "true" EDPs. The results show that the retrieved NmF2 and hmF2 are generally in good agreement with the true values, but the reliability of the retrieved Electron Density degrades in low latitude regions and at low altitudes. Specifically, the Abel retrieval method overestimates Electron Density to the north and south of the crests of the equatorial ionization anomaly (EIA), and introduces artificial plasma caves underneath the EIA crests. At lower altitudes (E- and F1-regions), it results in three pseudo peaks in daytime Electron densities along the magnetic latitude and a pseudo trough in nighttime equatorial Electron densities.
S M Radicella - One of the best experts on this subject based on the ideXlab platform.
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an improved empirical formulation of an ionosphere bottomside Electron Density profile thickness parameter
Advances in Space Research, 2017Co-Authors: K Alazocuartas, S M RadicellaAbstract:Abstract An improved empirical formulation for the characterization of the “base point” of the bottomside ionospheric Electron Density profile is proposed. The “base point” in an ionospheric layer is defined by the Electron Density profile height where the gradient dN/dh reaches a maximum. The difference between the height of the maximum Electron Density and the height of the “base point” is proportional to the ionospheric F2 layer thickness parameter B2. The previous empirical formula links the maximum value of dN/dh to foF2 and M(3000)F2 scaled from the ionograms. The new formulation adds a dependence on the solar zenith angle. The use of the new equation improves substantially the calculation of the B2 thickness parameter used in the NeQuick model.
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a near real time model assisted ionosphere Electron Density retrieval method
Radio Science, 2006Co-Authors: B Nava, R. Leitinger, S M Radicella, P CoissonAbstract:[1] NeQuick is a three-dimensional and time-dependent quick run Electron Density model specifically designed for transionospheric propagation applications. It allows calculation of Electron concentration values at any location in the ionosphere and the total Electron content (TEC) along any ground station–to–satellite ray path. After specific adaptations, the model has been used to develop a near-real-time nontomographic Electron Density retrieval technique able to provide the Electron Density of the ionosphere above the geographic area of interest. The technique relies on the knowledge of the model driving parameter Az (ionization level) for the location considered. In the present study, the necessary Az values have been obtained through direct ingestion of Global Positioning System (GPS)–derived slant TEC data in two different ways: using data from a single GPS receiver and using data from multiple ground stations. Statistical comparisons between experimental and reconstructed slant TEC values and between experimental and retrieved maximum Electron concentration values are shown.
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use of total Electron content data to analyze ionosphere Electron Density gradients
cosp, 2006Co-Authors: B Nava, R. Leitinger, S M Radicella, P CoissonAbstract:Abstract In the presence of Electron Density gradients the thin shell approximation for the ionosphere, used together with a simple mapping function to convert slant total Electron content (TEC) to vertical TEC, could lead to TEC conversion errors. These “mapping function errors” can therefore be used to detect the Electron Density gradients in the ionosphere. In the present work GPS derived slant TEC data have been used to investigate the effects of the Electron Density gradients in the middle and low latitude ionosphere under geomagnetic quiet and disturbed conditions. In particular the data corresponding to the geographic area of the American Sector for the days 5–7 April 2000 have been used to perform a complete analysis of mapping function errors based on the “coinciding pierce point technique”. The results clearly illustrate the Electron Density gradient effects according to the locations considered and to the actual levels of disturbance of the ionosphere. In addition, the possibility to assess an ionospheric shell height able to minimize the mapping function errors has been verified.
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topside Electron Density in iri and nequick features and limitations
Advances in Space Research, 2006Co-Authors: P Coisson, R. Leitinger, S M Radicella, B NavaAbstract:The topside ionosphere modeling suffers from the relative scarcity of experimental Electron Density data. Different modeling approaches have been applied in empirical models, like IRI, and profilers, like NeQuick. Comparing ISIS-2 topside Electron Density profiles with IRI and NeQuick models weak points in their topside formulation are identified and analysed. The IRI topside consists in two constant gradient sections, with a transition height kept at a fixed height in its domain. Tests of transition height and gradient modifications are presented, based on experimental evidences and model efforts. NeQuick model has a topside formulation based on a semi-Epstein layer, governed by an empirical shape parameter k. An alternative formulation is presented based on k values derived from experimental profiles.
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ionospheric topside models compared with experimental Electron Density profiles
EGS - AGU - EUG Joint Assembly, 2005Co-Authors: P Coisson, S M RadicellaAbstract:Recently an increasing number of topside Electron Density profiles has been made available to the scientific community on the Internet. These data are important for ionospheric modeling purposes, since the experimental information on the Electron Density above the ionosphere maximum of ionization is very scarce. The present work compares NeQuick and IRI models with the topside Electron Density profiles available in the databases of the ISIS2, IK19 and Cosmos 1809 satellites. Experimental Electron content from the F2 peak up to satellite height and Electron densities at fixed heights above the peak have been compared under a wide range of different conditions. The analysis performed points out the behavior of the models and the improvements needed to be assessed to have a better reproduction of the experimental results. NeQuick topside is a modified Epstein layer, with thickness parameter determined by an empirical relation. It appears that its performance is strongly affected by this parameter, indicating the need for improvements of its formulation. IRI topside is based on Booker’s approach to consider two parts with constant height gradients. It appears that this formulation leads to an overestimation of the Electron Density in the upper part of the profiles, and overestimation of TEC.
James L. Walsh - One of the best experts on this subject based on the ideXlab platform.
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Electron Density measurement in atmospheric pressure plasma jets stark broadening of hydrogenated and non hydrogenated lines
Plasma Sources Science and Technology, 2015Co-Authors: Yu A Nikiforov, C Leys, Manuel A Gonzalez, James L. WalshAbstract:Electron Density is one of the key parameters in the physics of a gas discharge. In this contribution the application of the Stark broadening method to determine the Electron Density in low temperature atmospheric pressure plasma jets is discussed. An overview of the available theoretical Stark broadening calculations of hydrogenated and non-hydrogenated atomic lines is presented. The difficulty in the evaluation of the fine structure splitting of lines, which is important at low Electron Density, is analysed and recommendations on the applicability of the method for low ionization degree plasmas are given. Different emission line broadening mechanisms under atmospheric pressure conditions are discussed and an experimental line profile fitting procedure for the determination of the Stark broadening contribution is suggested. Available experimental data is carefully analysed for the Stark broadening of lines in plasma jets excited over a wide range of frequencies from dc to MW and pulsed mode. Finally, recommendations are given concerning the application of the Stark broadening technique for the estimation of the Electron Density under typical conditions of plasma jets.
