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Regional ionospheric Total Electron Content (TEC) models are most significant to investigate the variability of ionosphere during all-weather conditions. Since the ground-based TEC measurements are not available in oceanic and polar regions, space-based observations are incorporated to increase the positional accuracy and reliability of Global Ionospheric TEC Maps (GIMs). Therefore, data fusion techniques are necessary to enhance the prediction capability of regional ionospheric models by considering multi-source data. In view of this, an attempt is made to investigate Equatorial Ionization Anomaly (EIA) structures in low-latitudinal Indian region using multi-instrument data. Data observations from background model CODEGIM, available International GNSS Service (IGS) stations in India, GNSS receivers at KLEF and Tripura stations, FORMOSAT/COSMIC radio occultation and SWARM during geomagnetic storm period August 26–28, 2021 are used for the study. Spherical Harmonics Function (SHF) of order 4 is employed along with Weighted Least Squares analysis (WLS), where separate weight constraint is computed for each data source. TEC maps of spatial resolution 5° x 5° and temporal resolution of 1 h are generated to illustrate the dynamic behavior of ionosphere. The standard deviation for 3 days is obtained as 0.42, 0.61 and 1.43 TECU respectively. TEC depletions and enhancements are observed on August 27 and 28, with mean values of 12.74 and 15.27 TECU respectively, demonstrating negative and positive storm effects. [ABSTRACT FROM AUTHOR]

Existing ionospheric models perform very well in mapping the calm state of the ionosphere. However, the problem is accurately determining the total electron content (TEC) for disturbed days. Knowledge of the exact electron density is essential for single−frequency receivers, which cannot eliminate the ionospheric delay. This study aims to investigate temporal and spatial variability in the distribution of TEC based on differences between maps of individual Ionospheric Associated Analysis Centers (IAACs) of the International GNSS Service (IGS) and aligned altimetry−TEC from 2005–2021. Based on the temporal distribution, we have observed a significant effect of solar activity on the mean and standard deviation behavior of the differences between global ionospheric maps (GIMs) and Jason−derived TEC. We determined the biases for the entire calculation period, through which it can be concluded that the upcg-Jason and igsg-Jason differences have the lowest standard deviation (±1.81 TECU). In addition, the temporal analysis made it possible to detect annual, semi−annual, and 117-day oscillations occurring in the Jason−TEC data, as well as 121-day oscillations in the GIMs. It also allowed us to analyze the potential sources of these cyclicities, solar and geomagnetic activity, in the case of the annual and semi−annual periodicities. When considering spatial variations, we have observed that the most significant average differences are in the intertropical areas. In contrast, the smallest differences were recorded in the southern hemisphere, below the Tropic of Capricorn (23.5°S). However, the slightest variations were noted for the northern hemisphere above the Tropic of Cancer (23.5°N). Our research presented in this paper allows a better understanding of how different methods of GNSS TEC approximation affect the model's accuracy. [ABSTRACT FROM AUTHOR]

This work presents the potential for using pulsed gas injection to produce amorphous carbon films. In this experiment, the frequency of injecting small amounts of gas was used to control the pressure amplitudes, thus achieving the conditions of plasma generation from stationary, through quasi-stationary, to pulsed oscillations of pressure. In addition, we used various gases and their mixtures, an alternative to argon. In the experiment, we studied the energy state of the plasma. The films were examined for phase and chemical composition, surface morphology, and optical and mechanical properties. We determined low-frequency pulsed gas injections to be conditions favorable for C (s p 3) − C (s p 3) bond formation. The plasma generated by gas injections is better ionized than that generated by static pressure. Pulsed conditions favor the plasma species to retain their kinetic energy, limiting the probability of intermolecular collision events. Since helium has a relatively high ionization energy, it is a practical addition to sputtering gas because of the increasing sp3 content in the films. The electrons created by helium ionization improve the plasma's ionization degree. [ABSTRACT FROM AUTHOR]

Existing ionospheric models perform very well in mapping the calm state of the ionosphere. However, the problem is accurately determining the total electron content (TEC) for disturbed days. Knowledge of the exact electron density is essential for single−frequency receivers, which cannot eliminate the ionospheric delay. This study aims to investigate temporal and spatial variability in the distribution of TEC based on differences between maps of individual Ionospheric Associated Analysis Centers (IAACs) of the International GNSS Service (IGS) and aligned altimetry−TEC from 2005–2021. Based on the temporal distribution, we have observed a significant effect of solar activity on the mean and standard deviation behavior of the differences between global ionospheric maps (GIMs) and Jason−derived TEC. We determined the biases for the entire calculation period, through which it can be concluded that the upcg-Jason and igsg-Jason differences have the lowest standard deviation (±1.81 TECU). In addition, the temporal analysis made it possible to detect annual, semi−annual, and 117-day oscillations occurring in the Jason−TEC data, as well as 121-day oscillations in the GIMs. It also allowed us to analyze the potential sources of these cyclicities, solar and geomagnetic activity, in the case of the annual and semi−annual periodicities. When considering spatial variations, we have observed that the most significant average differences are in the intertropical areas. In contrast, the smallest differences were recorded in the southern hemisphere, below the Tropic of Capricorn (23.5°S). However, the slightest variations were noted for the northern hemisphere above the Tropic of Cancer (23.5°N). Our research presented in this paper allows a better understanding of how different methods of GNSS TEC approximation affect the model’s accuracy.

This paper presents the experimental results of high-temperature sputtering of nickel targets by the Gas Injection Magnetron Sputtering (GIMS) technique. The GIMS technique is a pulsed magnetron sputtering technique that involves the generation of plasma pulses by injecting small doses of gas into the zone of the magnetron target surface. Using a target with a dedicated construction to limit heat dissipation and the proper use of injection parameters and electrical power density, the temperature of the target during sputtering can be precisely controlled. This feature of the GIMS technique was used in an experiment with sputtering nickel targets of varying thicknesses and temperatures. Plasma emission spectra and current-voltage waveforms were studied to characterize the plasma process. The thickness, structure, phase composition, and crystallite size of the nickel layers produced on silicon substrates were investigated. Our experiment showed that although the most significant increase in growth kinetics was observed for high temperatures, the low sputtering temperature range may be the most interesting from a practical perspective. The excited plasma has the highest energy in the sputtering temperature range, just above the Curie temperature. [ABSTRACT FROM AUTHOR]

Single-frequency precise point positioning (PPP) is widely used with the advantage of cost-efficient, while its further development and application are limited by the difficulty of ionospheric delay correction and the long-time convergence, especially for real-time positioning. And the development of high-accuracy ionospheric models plays an important role for the correction of ionospheric delay in single-frequency PPP. In this paper, the final and rapid global ionospheric map (GIM) products released by Chinese Academy of Science (CAS), Center for Orbit Determination in Europe (CODE), European Space Agency (ESA), Jet Propulsion Laboratory (JPL), Universitat Politècnica de Catalunya (UPC), Wuhan University (WHU) and International GNSS Service (IGS) were used as external constraints in static, simulation kinematic and kinematic single-frequency PPP respectively. The performance and practicality of each product were analyzed by using IGS station observation data (September 2017 and January 2018, with different ionospheric activity levels) and a kinematic experiment. The results indicate that GIM products may improve convergence time in most areas of middle and high latitudes of the globe. However, the improvement of convergence time of some regions in low latitudes or near the equator with dense and uniform distributed IGS stations show even better performance than the regions in middle and high latitudes. Comparing with standard PPP (S-PPP), the convergence time of static PPP is reduced about 14–42% and 13–29% with GIM final and rapid products respectively. In simulation kinematic PPP, the convergence time improves 10–43% and 12–25% for final and rapid products respectively. In the kinematic positioning, the addition of external ionospheric constraints may speed up the convergence in the early stage of positioning and improve the accuracy to a certain extent. Among all GIM products, the final products show better performance than that of the rapid products obviously. The GIM products from CAS and CODE and UQRG from UPC express the best performance are recommended to process ionospheric delay in the high-accuracy positioning. [ABSTRACT FROM AUTHOR]

In this work, the Global Ionospheric Maps (GIMs) are used to analyze the behavior of the mid-latitude ionospheric trough (MIT) during the solar cycle 24 (2008–2019). This analysis is performed for the Northern and Southern Hemispheres at different local times: 00, 02 and 04 LT. We study the MIT position dependence on the phase of the solar cycle, seasonal, and geomagnetic activity during the post-midnight period. We find that the MIT position shows an interhemispheric asymmetry. Its equatorward movement from low to high solar activity is about 3 ° and 1 ° for Northern and Southern Hemisphere respectively for the three local times analyzed. There is also a clear seasonal variation, the shift between winter and summer is around 3 ° and 1 ° at 00 LT and 6 ° and 4 ° at 04 LT for the Northern and Southern Hemispheres, respectively. In general, the MIT position reaches the highest geomagnetic latitude in winter, without variation with local time. However, in summer it takes the lowest geomagnetic latitude, moving towards the equator from 00LT to 04LT. The MIT position moves equatorward under disturbed geomagnetic conditions, and the difference between the MIT position during quiet and perturbed days is greater in the Northern than in the Southern Hemisphere. In addition, the periodicity of the variability of the MIT position for both Hemispheres versus the solar wind speed and IMF Bz-component are analyzed using the wavelet transform, showing a clear dependence between them during the descending and minimum solar phase at 13.5 and 27-day time scales. [ABSTRACT FROM AUTHOR]

A new approach is proposed for the global ionospheric modeling using epoch-by-epoch estimation. The GIMs with a high temporal resolution are greatly useful for studying the climatology and weather of the ionosphere, including ionospheric variations, such as noon-time bite-outs and nighttime enhancements.

The aim of this work is the analysis of the mid-latitude ionospheric trough (MIT) using the Global Ionospheric Maps from IGS (GIMs) during the solar minimum, year 2008. This study was performed for different local times, 22, 00, 02 and 04 LT on the Northern and Southern hemisphere simultaneously. In the two hemispheres the MIT show asymmetric pattern. The high-latitude troughs are clearly distinguished in autumn and winter. Another feature is the longitudinal development towards the west of the geomagnetic pole covering a wider area in the Northern Hemisphere. Five empirical reference models were tested and compared with the MIT minimum position obtained from GIMs at different local times for both hemisphere. The results show a better agreement with the observations for the Northern Hemisphere specially with the Köehnlein & Raitt model. Fluctuations of 9 days and 27 days of the MIT minimum position are found, which could be related with the solar wind oscillations, especially for 00 and 02 LT in both hemisphere, suggesting a link between them. [ABSTRACT FROM AUTHOR]

In this study, thin Al2O3 films (11 nm – 82 nm) were deposited by means of a recently developed pulse gas injection magnetron sputtering method and investigated by means of atomic force microscopy, spectroscopic ellipsometry and spectrophotometry. Quite low values of optical constants (1.581 to 1.648 at λ = 550 nm) of the alumina films are directly associated with specific growth conditions (pulse injection of the reactive or reactive + inert gas) in the pulse gas injection magnetron sputtering process. The light transmittance of Al2O3/glass systems (86 % to 90 %) is only a few percent lower than that calculated for glass (93 %). [ABSTRACT FROM AUTHOR]

Abstract: The objective of this paper is threefold: (1) To present a working methodology for the combined use of modeling technology and microwave remote-sensing measurements in the assessment of attenuation of electromagnetic waves by the vegetation cover; (2) To illustrate this methodology with computer calculations of the attenuation for various soil-plant formations; (3) To give a perspective of the developed methodology applied to the study of global environmental change, including the radiative forcing problem. [Copyright &y& Elsevier]

• A new approach for global ionospheric modeling with high temporal resolution is proposed. • Global ionospheric maps with high temporal resolution (30 s) are generated. • Several ionospheric anomalies can be clearly seen in the GIMs with high temporal resolution, but not observed by the traditional GIMs with 1-h or 2-h resolution. A new approach is proposed for the global ionospheric modeling using epoch-by-epoch estimation. The GIMs with a high temporal resolution are greatly useful for studying the climatology and weather of the ionosphere, including ionospheric variations, such as noon-time bite-outs and nighttime enhancements. [ABSTRACT FROM AUTHOR]