A new version of the NeQuick ionosphere electron density model (original) (raw)
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An improved bottomside for the ionospheric electron density model NeQuick
2005
The ionospheric electron density model NeQuick is a «profiler» which uses the peaks of the E-layer, the F1-layer and the F2-layer as anchor points. In the version prepared for and submitted to the International Telecommunication Union (ITU) the model uses the ITU-R (CCIR) maps for foF2 and M(3000)F2 and adapted maps similar to the ITU-R ones for foE and foF1. Since users found problematic behaviour of NeQuick under conditions of strong differences of foE and foF2 map structures, the profiling was adapted by changing the properties of the Epstein layers used for this purpose. The new formulation avoids both strange horizontal structures of the geographic distribution of electron density in fixed heights and unrealistic peculiarities of the height profile which occasionally occurred with the old version of the model. Since the Epstein layer approach allows for 8 parameters only (3 layer amplitudes and 5 semi-thicknesses) the adaptation was no minor task but needed careful planning of suitable strategies.
Topside ionosphere and plasmasphere: Use of NeQuick in connection with Gallagher plasmasphere model
Advances in Space Research, 2007
The NeQuick ionospheric electron density model has a very simple topside formulation, which allows taking into account the electron content up to 20,000 km. In the present work, the Gallagher model has been used in connection with NeQuick to provide a more realistic representation of the electron concentration distribution in the plasmasphere. An analysis of the impact of the proposed modification in low geomagnetic latitudes (±40°) on modeled vertical total electron content has been performed for different levels of solar activity, season, and universal time.
Total electron content models and their use in ionosphere monitoring
Radio Science, 2011
1] In Global Navigation Satellite Systems (GNSS) using L band frequencies, the ionosphere causes signal delays that correspond to link-related range errors of up to 100 m. Whereas this error can be corrected in dual-frequency measurements by a linear combination of L1 and L2 phases, in single-frequency measurements, additional information is needed to mitigate the ionospheric error which is proportional to the total electron content (TEC) of the ionosphere. This information can be provided by TEC maps deduced from corresponding GNSS measurements or from model values. Besides direct range error correction in navigation and remote sensing applications, TEC or electron density models play a key role in ionospheric monitoring and forecasting. In this paper we discuss the development and use of TEC models for calibrating TEC, reconstructing reliable TEC maps, and forecasting TEC behavior based on GNSS measurements. European and global TEC maps and corresponding 1 h ahead forecasts are distributed via the operational space weather and ionosphere data service (http://swaciweb.dlr.de) to the international community. The Neustrelitz TEC Model is a basic approach for a family of regional and global TEC models used in different types of applications. The model approximates typical TEC variations depending on the location, time, and level of solar activity with only a few coefficients. Citation: Jakowski, N., C. Mayer, M. M. Hoque, and V. Wilken (2011), Total electron content models and their use in ionosphere monitoring, Radio Sci., 46, RS0D18,
TEC ingestion into NeQuick 2 to model the topside electron density in the East-African ionosphere
This study investigates the performances of the NeQuick 2 empirical model in the East-African region by assisting this model with Global Positioning System (GPS) measurements obtained from a single station. First we calculate an effective ionization level that drives NeQuick 2 to reproduce TEC that fits the least square sense to the measurements. We then quantify the performances of the NeQuick 2 in reproducing the topside in situ ion density observed by Communication/ Navigation Outage Forecast System (C/NOFS) satellite after modifying the model's input parameter. This is done by inputting the effective ionization level calculated from the slant total electron content (sTEC) measurements obtained from the single GPS receiver to the model. The performances of the model before and after data ingestion are then investigated by comparing the model results with the topside in situ ion density observation. One-month data during low solar activity conditions were used in this study. W...
A family of ionospheric models for different uses
Physics and Chemistry of The Earth Part C-solar-terrestial and Planetary Science, 2000
Empirical models of three dimensional electron density distributions in the ionosphere have been constructed for global as wel1 as regional use. The models differ by their degree of complexity and calculation time and therefore have different uses. Al1 are based on "ionogram parameter" (critical frequenties foE, foF1, foF2 and the F2 region transfer parameter M(3000)F2). The models allow the use of global or regional maps for foF2 and M(3000)F2 and use built-in formulations for foE and foF1. Update (instantaneous mapping / nowcasting) versions exist which take foF2 and M(3000)F2 or F2 region peak height and electron density as input. The ground to F2 layer peak part of the profile is identical for al1 three models and is based on an Epstein formulation. The "quick calculation" model NeQuick uses a simple formulation for the topside F layer, which is essentially a semi-Epstein layer with a thickness parameter which increases linearly with height. The "ionospheric model" COSTprof is the model which was adopted by COST 251 in its regional "monthly median" form. Its topside F layer is based on O+-H+ diffusive equilibrium with built-in maps for three parameters, namely the oxygen scale height at the F2 peak, its height gradient and the O+-H+ transition height. The "ionosphereplasmasphere" model NeUoG-plas uses a magnetic field aligned "plaSmasphere" above COSTprof.
Annals of …, 2005
A technique to reconstruct the electron density of the ionosphere starting from total electron content values has been developed using the NeQuick ionospheric electron density model driven by its effective ionization parameter Az. The technique is based on the computation of Az values for a suitable worldwide grid of points. A simple way to obtain relevant Az grids is to use global vertical Total Electron Content (TEC) maps to define for each grid point as Az value, the one that minimizes the difference between the experimental and the modeled vertical TEC. Having a global grid of Az values it is possible to compute the electron density at any point in the ionosphere using NeQuick. As a consequence, slant TEC values for specific ground station to satellite links or ionosphere peak parameter values at any location can be calculated. The results of the comparisons between experimental and reconstructed slant TEC as well as experimental and reconstructed peak parameters values indicate that the proposed reconstruction method can be used to reproduce the observed ionosphere in a realistic way.
A global empirical model of the ionospheric topside electron density
Advances in Space Research, 2004
As it was mentioned in many publications, the Bent model for the topside ionosphere used in IRI is not adequate, especially for the periods of high solar activity. Additional efforts are necessary to improve the empirical presentation of the electron concentration vertical distribution in topside ionosphere. The present paper is review of attempts to create the empirical model of the topside vertical profile undertaken within the frame of IRI Task Force Activity Workshops held at ICTP, Trieste. The Intercosmos-19 topside profiles database was used. The profile was approximated by Epstein function with the altitude dependent F2 layer thickness parameter B 2u . The main task was to find if the latitudinal dependencies of the model parameters have the regular character. The model was presented as the set of coefficients characterizing the profile for different latitudes, season and local time. Up to now the model is limited by the period of high solar activity. Attempts were made on revealing the longitudinal dependencies and its inclusion in the model.
A new climatological electron density model for supporting space weather services
Journal of Space Weather and Space Climate, 2021
The ionosphere is the ionized part of the Earth atmosphere, ranging from about 60 km up to several Earth radii whereas the upper part above about 1000 km height up to the plasmapause is usually called the plasmasphere. We present a new three-dimensional electron density model aiming for supporting space weather services and mitigation of propagation errors for trans-ionospheric signals. The model is developed by superposing the Neustrelitz Plasmasphere Model (NPSM) to an ionosphere model composed of separate F and E-layer distributions. It uses the Neustrelitz TEC model (NTCM), Neustrelitz Peak Density Model (NPDM) and the Neustrelitz Peak Height Model (NPHM) for the total electron content (TEC), peak ionization and peak height information. These models describe the spatial and temporal variability of the key parameters as function of local time, geographic/geomagnetic location, solar irradiation and activity. The model is particularly developed to calculate the electron concentrati...
A near-real-time model-assisted ionosphere electron density retrieval method
Radio Science, 2006
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.
Ionospheric Correction Based on Ingestion of Global Ionospheric Maps into the NeQuick 2 Model
TheScientificWorldJournal, 2015
The global ionospheric maps (GIMs), generated by Jet Propulsion Laboratory (JPL) and Center for Orbit Determination in Europe (CODE) during a period over 13 years, have been adopted as the primary source of data to provide global ionospheric correction for possible single frequency positioning applications. The investigation aims to assess the performance of new NeQuick model, NeQuick 2, in predicting global total electron content (TEC) through ingesting the GIMs data from the previous day(s). The results show good performance of the GIMs-driven-NeQuick model with average 86% of vertical TEC error less than 10 TECU, when the global daily effective ionization indices (Az) versus modified dip latitude (MODIP) are constructed as a second order polynomial. The performance of GIMs-driven-NeQuick model presents variability with solar activity and behaves better during low solar activity years. The accuracy of TEC prediction can be improved further through performing a four-coefficient fun...