Correlation between ionospheric models and space weather indices for 2011 (original) (raw)
Related papers
Key words ionospheric model – model assessment – model uses
The genesis and evolution of the NeQuick model is reviewed from the initial ionospheric efforts made in the framework of the European COST actions on ionospheric issues to the last version of the model (NeQuick 2). Attention is given to the uses of the model particularly by the European satellite navigation and positioning systems EGNOS and GALILEO. Recent assessment studies on the performance of NeQuick 2 are also reviewed.
Global models of the ionosphere obtained by integration of GNSS and satellite altimetry data
2007
The high free-electron and ion density in the ionosphere disturbs both the group and phase velocity of the signals of all space geodetic techniques, operating in the microwave band. In first approximation this delay is proportional to the socalled Slant Total Electron Content (STEC) along the ray path and can be corrected only if the measurements are carried out at two distinct frequencies. On the other hand, this effect allows information to be gained about the parameters of the ionosphere in terms of Total Electron Content (TEC) values. The classical input data for the development of Global Ionosphere Maps (GIM) of the total electron content is obtained from dual-frequency Global Navigation Satellite System (GNSS) observations. However, the GNSS stations are inhomogeneously distributed, with large gaps particularly over the sea surface, which lowers the precision of the GIM over these areas. On their part, dualfrequency satellite altimetry missions such as Jason-1 provide information about the ionosphere precisely above the sea surface. Due to the limited spread of the measurements and some open questions related to their systematic errors, the ionospheric data from satellite altimetry is used only for cross-validation of the GNSS GIM so far. It can be anticipated however, that some specifics of the ionosphere parameters derived by satellite altimetry will partly balance the inhomogeneity of the GNSS data. In this study we create two-hourly GIM from GNSS data and additionally introduce satellite altimetry observations, which help to compensate the insufficient GNSS coverage of the oceans. Furthermore, this method allows the independent estimation of systematic instrumental errors, affecting the two types of measurements. Thus, besides the daily values of the Differential Code Biases (DCB) for all GNSS satellites and receivers, also a constant daily bias for the Jason-1 satellite is estimated and investigated.
Ionospheric and Tropospheric Modelling and Monitoring for GNSS at the European Space Agency
This paper summarizes recent activities in the area of tropospheric and ionospheric research undertaken by ESA in support of the development and qualification of the European Geostationary Navigation Overlay Service (EGNOS) and of the GALILEO system. Experimentation is needed to verify and validate the models used for describing the temporal and spatial variability of atmospheric conditions influencing the propagation conditions. For Satellite navigation, propagation effects may impact user accuracy, integrity, availability or continuity of service. Those impairments may also impact system performance by affecting the ground of the Navigation system such as sensor station observations. One of the key propagation effects is the tropospheric and ionospheric group delay. But also the presence of ionospheric scintillations can impact on the performance and continuity of navigation services and need to be well understood.
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...
International Reference Ionosphere 2007: Improvements and new parameters
Advances in Space Research, 2008
The International Reference Ionosphere (IRI), a joint project of URSI and COSPAR, is the de facto international standard for the climatological specification of ionospheric parameters and as such it is currently undergoing registration as Technical Specification (TS) of the International Standardization Organization (ISO). IRI by charter and design is an empirical model based on a wide range of ground and space data. It describes monthly averages of ionospheric densities and temperatures in the altitude range 50-1500 km in the non-auroral ionosphere. Since its inception in 1969 the IRI model has been steadily improved with newer data and with better mathematical descriptions of global and temporal variation patterns. A large number of independent studies have validated the IRI model in comparisons with direct and indirect ionospheric measurements not used in the model development. A comparison with IRI is often one of the first science tasks by an ionospheric satellite or rocket team. This paper describes the latest version of the IRI model, IRI-2007, explaining the most important changes that are being introduced with this version. These include: (1) two new options for the topside electron density, (2) a new model for the topside ion composition, (3) the first-time inclusion of a model for the spread F occurrence probability, (4) a NeuralNet model for auroral E-region electron densities, (5) a model for the plasmaspheric electron temperature, and (6) the latest International Geomagnetic Reference Field (IGRF) model for the computation of magnetic coordinates including their changes due to the secular variation of the magnetic field.
Study of Ionospheric Variability Using GNSS Observations
2018
International audienceWith the increasing number of applications of Global navigation satellite system, the modeling of the ionosphere is a crucial element for precise positioning. Indeed, the ionosphere delays the electromagnetic waves which pass through it and induces a delay of propagation related to the electronic density (TEC) Total Electronic Content and to the frequency of the wave. The impact of this ionospheric error often results in a poor determination of the stations position, particularly in strong solar activity. The first part of this paper focuses on a bibliographic study oriented first of all on the study of the ionosphere in relation to solar activity and secondly on the determination of the total electron content using GNSS measurements from the IGS network reference stations. Measurements were made on two permanent stations RABT, TETN. We selected years of GNSS measurements to evaluate the geomagnetic impact on the ionosphere, 2001, 2009 and 2013. A description o...
Nequick2 Model Behaviour for Global Ionospheric Delay Mitigation During Solar Cycle-24
Artificial Satellites
The ionospheric delay is the major current source of potential range delay for single-frequency GNSS users. Different ionospheric delay mitigation methods have been developed to mitigate the ionospheric delay effects for single-frequency users. The NeQuick is a quick-run ionospheric electron density model particularly designed for trans-ionospheric propagation applications developed at the Aeronomy and Radio propagation Laboratory of the Abdus Salam International Centre for Theoretical Physics (ICTP), Italy. NeQuick2 is the latest version of the NeQuick ionosphere electron density model. NeQuick model been used by the European Space Agency (ESA) European Geostationary Navigation Overlay Service (EGNOS) project for assessment analysis and has been adopted for single-frequency positioning applications in the frame work of the European satellite navigation system (Galileo). NeQuick2 model adopted modifications related to the modeling of the F1 layer peak electron density, height and th...
Remote Sensing
Users of the global navigation satellite system (GNSS) operating with a single-frequency receiver must use an ionospheric correction algorithm (ICA) to account for the delay introduced on radio waves by the upper atmosphere. Galileo, the European GNSS, uses an ICA named NeQuick-G. In an effort to foster the adoption of NeQuick-G by final users, two implementations in C language have been recently made available to the public by the European Space Agency (ESA) and the Joint Research Centre (JRC) of the European Commission (EC), respectively. The aim of the present contribution is to compare the slant total electron content (STEC) predictions of the two aforementioned implementations of NeQuick-G. For this purpose, we have used actual multi-constellation and multi-frequency data for several hundreds of stations distributed worldwide belonging to the Multi GNSS Experiment (MGEX) network of the International GNSS Service (IGS). For each first day of the month during year 2019, the STECs...
COMPARISON OF GPS/GALILEO SINGLE FREQUENCY IONOSPHERIC MODELS WITH VERTICAL TEC MAPS
The ionospheric delay is the major current source of potential range delay for single-frequency GNSS users (Kunches and Klobuchar, 2001). Single-frequency GNSS users are in most need of an ionospheric model to eliminate the ionospheric delay to a high degree of accuracy. GPS system uses the Klobuchar model for this task, which its coefficients are sent through the GPS navigation message to GPS users. Klobuchar model uses the Ionospheric Corrections Algorithm (ICA) (Klobuchar, 1987) designed to account for approximately 50% (rms) of the ionospheric range delay. NeQuick model is a model of the electron concentration profile that has been developed in the framework of the European Commission COST action 251. NeQuick model is being proposed for single-frequency operation in the European Galileo GNSS system (Radicella et al., 2003). A comparison study between the behaviour of the GPS Single-frequency ionospheric modelling (Klobuchar model) and the Galileo proposed approach for this task (NeQuick model) will be presented in this paper. The range delay correction by the two models has been assessed using the IGSGlobal Ionospheric Maps for three different-latitude stations to reflect different geographic ionospheric activity states. The study was carried out over three different months that each of them reflects a different state of solar activity, which is a major indication for the ionospheric development state.