scholarly journals Integrity investigation of global ionospheric TEC maps for high-precision positioning

2021 ◽  
Vol 95 (3) ◽  
Author(s):  
Jiaojiao Zhao ◽  
Manuel Hernández-Pajares ◽  
Zishen Li ◽  
Ningbo Wang ◽  
Hong Yuan
Keyword(s):  
Solar Activity ◽  
Geomagnetic Storm ◽  
Precise Point Positioning ◽  
Electron Content ◽  
International Gnss Service ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
Actual Error ◽  
Minimum Solar Activity ◽  
Global Ionospheric Maps

AbstractAside from the ionospheric total electron content (TEC) information, root-mean-square (RMS) maps are also provided as the standard deviations of the corresponding TEC errors in global ionospheric maps (GIMs). As the RMS maps are commonly used as the accuracy indicator of GIMs to optimize the stochastic model of precise point positioning algorithms, it is of crucial importance to investigate the reliability of RMS maps involved in GIMs of different Ionospheric Associated Analysis Centers (IAACs) of the International GNSS Service (IGS), i.e., the integrity of GIMs. We indirectly analyzed the reliability of RMS maps by comparing the actual error of the differential STEC (dSTEC) with the RMS of the dSTEC derived from the RMS maps. With this method, the integrity of seven rapid IGS GIMs (UQRG, CORG, JPRG, WHRG, EHRG, EMRG, and IGRG) and six final GIMs (UPCG, CODG, JPLG, WHUG, ESAG and IGSG) was examined under the maximum and minimum solar activity conditions as well as the geomagnetic storm period. The results reveal that the reliability of the RMS maps is significantly different for the GIMs from different IAACs. Among these GIMs, the values in the RMS maps of UQRG are large, which can be used as ionospheric protection level, while the RMS values in EHRG and ESAG are significantly lower than the realistic RMS. The rapid and final GIMs from CODE, JPL and WHU provide quite reasonable RMS maps. The bounding performance of RMS maps can be influenced by the location of the stations, while the influence of solar activity and the geomagnetic storm is not obvious.

scholarly journals Probing the ionosphere by the pulsar B0950+08 with help of RadioAstron ground-space baselines

2019 ◽  
Vol 491 (4) ◽  
pp. 5843-5851
Author(s):  
Vladimir I Zhuravlev ◽  
Yu I Yermolaev ◽  
A S Andrianov
Keyword(s):  
Geomagnetic Storm ◽  
Radio Telescope ◽  
Preliminary Analysis ◽  
Very Long Baseline Interferometry ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Total Electron ◽  
Space Radio Telescope ◽  
Long Baseline ◽  
Ionospheric Total Electron Content

ABSTRACT The ionospheric scattering of pulses emitted by PSR B0950+08 is measured using the 10-mRadioAstron Space Radio Telescope, the 300-m Arecibo Radio Telescope, and the 14 x 25-m Westerbork Synthesis Radio Telescope (WSRT) at a frequency band between 316 and 332 MHz. We analyse this phenomenon based on a simulated model of the phase difference obtained between antennas that are widely separated by nearly 25 Earth diameters. We present a technique for processing and analysing the ionospheric total electron content (TEC) at the ground stations of the ground-space interferometer. This technique allows us to derive almost synchronous half-hour structures of the TEC in the ionosphere at an intercontinental distance between the Arecibo and WSRT stations. We find that the amplitude values of the detected structures are approximately twice as large as the values for the TEC derived in the international reference ionosphere (IRI) project. Furthermore, the values of the TEC outside these structures are almost the same as the corresponding values found by the IRI. According to a preliminary analysis, the detected structures were observed during a geomagnetic storm with a minimum Dst index of ∼75 nT generated by interplanetary disturbances, and may be due to the influence of interplanetary and magnetospheric phenomena on ionospheric disturbances. We show that the Space Very Long Baseline Interferometry provides us with new opportunities to study the TEC, and we demonstrate the capabilities of this instrument to research the ionosphere.

scholarly journals Localized TEC enhancements in the Southern Hemisphere

2019 ◽  
Author(s):  
Ilya K. Edemskiy
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Southern Hemisphere ◽  
Occurrence Rate ◽  
Continuous Series ◽  
Electron Content ◽  
Field Orientation ◽  
Total Electron ◽  
Magnetic Field Orientation ◽  
Global Ionospheric Maps

Abstract. The paper is dedicated to investigation of localized TEC (total electron content) enhancements (LTEs), particularly of LTE series, detected in the Southern Hemisphere using global ionospheric maps for different solar activity years (2014, 2015, 2018). It is shown that LTE intensity varies in dependence on solar flux and does not directly depend on interplanetary magnetic field orientation. The enhancements occur in a subsolar region and could be observed during a continuous series of days. The highest LTE occurrence rate is observed during period of local winter (April-September) for all analyzed years. The longest observed LTE series was detected during 2014 and lasted 80 days or 120 days if we exclude 2 daily gaps.

Development and investigation of a deep learning based method for TEC map completion

2020 ◽  
Author(s):  
Mingwu Jin ◽  
Yang Pan ◽  
Shunrong Zhang ◽  
Yue Deng
Keyword(s):  
Solar Activity ◽  
Mean Squared Error ◽  
Image Inpainting ◽  
Science Research ◽  
High Solar Activity ◽  
Electron Content ◽  
International Gnss Service ◽  
Generative Adversarial Network ◽  
Total Electron ◽  
Adversarial Network

<p>Because of the limited coverage of receiver stations, current measurements of Total Electron Content (TEC) by ground-based GNSS receivers are not complete with large portions of data gaps. The processing to obtain complete TEC maps for space science research is time consuming and needs the collaboration of five International GNSS Service (IGS) Ionosphere Associate Analysis Centers (IAACs) to use different data processing and filling algorithms and to consolidate their results into final IGS completed TEC maps. In this work, we developed a Deep Convolutional Generative Adversarial Network (DCGAN) and Poisson blending model (DCGAN-PB) to learn IGS completion process for automatic completion of TEC maps. Using 10-fold cross validation of 20-year IGS TEC data, DCGAN-PB achieves the average root mean squared error (RMSE) about 4 absolute TEC units (TECu) of the high solar activity years and around 2 TECu for low solar activity years, which is about 50% reduction of RMSE for recovered TEC values compared to two conventional single-image inpainting methods. The developed DCGAN-PB model can lead to an efficient automatic completion tool for TEC maps.</p>

scholarly journals Redes neurais artificiais aplicadas na previsão do VTEC no Brasil

2013 ◽  
Vol 19 (2) ◽  
pp. 227-246 ◽  
Author(s):  
Wagner Carrupt Machado ◽  
Edvaldo Simões da Fonseca Junior
Keyword(s):  
Total Electron Content ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
International Gnss Service ◽  
Total Electron ◽  
De Se ◽  
Pierce Point ◽  
Global Ionospheric Maps

Uma forma de se prever o conteúdo total de elétrons na direção vertical (VTEC - Vertical Total Electron Content) usando a arquitetura de redes neurais artificiais (RNA) denominada de perceptrons de múltiplas camadas (MLP - MultipLayer Percetrons) é apresentada e avaliada nesta pesquisa. As entradas do modelo foram definidas como sendo a posição dos pontos ionosféricos (IPP - Ionospheric Pierce Point) e o tempo universal (TU), enquanto que a saída é o VTEC. As variações sazonais e de períodos mais longos são levadas em conta através da atualização do treinamento diariamente. Testes foram conduzidos sobre uma área que abrange o Brasil e sua vizinhança considerando períodos de alta e baixa atividade solar. As RNA foram treinadas utilizando informações dos mapas globais da ionosfera (GIM - Global Ionospheric Maps) produzidos pelo serviço internacional do GNSS (IGS - International GNSS Service) das 72 horas anteriores à época de início da previsão. As RNA treinadas foram utilizadas para prever o VTEC por 72 horas (VTEC RNA). Os VTEC RNA foram comparados com os VTEC contidos nos GIM (VTEC GIM). A raiz do erro médio quadrático (RMS) da diferença entre o VTEC GIM e o VTEC RNA variou de 1,4 a 10,7 unidades de TEC (TECU). O erro relativo mostra que a RNA proposta foi capaz de prever o VTEC com 70 a 85% de acerto.

scholarly journals Changes in the GNSS precise point positioning accuracy during a strong geomagnetic storm

2020 ◽  
Vol 196 ◽  
pp. 01001
Author(s):  
Anna Yasyukevich ◽  
Semen Syrovatskii ◽  
Yury Yasyukevich
Keyword(s):  
Geomagnetic Storm ◽  
Precise Point Positioning ◽  
Global Navigation Satellite Systems ◽  
Maximum Effect ◽  
Electron Content ◽  
Dual Frequency ◽  
Period Range ◽  
Positioning Accuracy ◽  
Total Electron ◽  
Point Positioning

Based on the data from dual-frequency receivers of global navigation satellite systems (GNSS), we analyze the changes in GNSS positioning accuracy during the August 25-26, 2018 strong geomagnetic storm on a global scale. The storm is one of the strongest geomagnetic events of the solar cycle 24. To analyze the positioning quality, we calculated coordinates using the precise point positioning (PPP) method in the kinematic mode. We recorder a significant degradation in the PPP positioning accuracy during the main phase of the storm. The maximum effect is observed in the middle and high latitudes of the US-Atlantic longitude sector. The average PPP error during the storm is shown to exceed ~0.5 m, that is up to 5 times higher than the values typical on quiet days. Areas with increased PPP errors is revealed to correspond to the regions with significant increase in the intensity of total electron content variations of 10–20 min period range. This increase is presumably due to the auroral oval expansion toward middle latitudes.

scholarly journals Status of CAS global ionospheric maps after the maximum of solar cycle 24

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Zishen Li ◽  
Ningbo Wang ◽  
Ang Liu ◽  
Yunbin Yuan ◽  
Liang Wang ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Single Layer ◽  
Latitudinal Gradients ◽  
Electron Content ◽  
International Gnss Service ◽  
Total Electron ◽  
Solar Cycle 24 ◽  
Cycle 24 ◽  
Global Ionospheric Maps

AbstractAs a new Ionosphere Associate Analysis Center (IAAC) of the International GNSS Service (IGS), Chinese Academy of Sciences (CAS) started the routine computation of the real-time, rapid, and final Global Ionospheric Maps (GIMs) in 2015. The method for the generation of CAS rapid and final GIMs and recent updates are presented in the paper. The quality of CAS post-processed GIMs is assessed during 2015–2018 after the maximum of solar cycle 24. To perform an independent and fair assessment, Jason-2/3 Vertical Total Electron Contents (VTEC) are first used as the references over the ocean. GPS differential Slant TECs (dSTEC) generated from 55 Multi-GNSS Experimental (MGEX) stations of the IGS are also employed, which provides a complementing way to evaluate the ability of electron content models to reproduce the spatial and temporal gradients in the ionosphere. During the test period, Jet Propulsion Laboratory (JPL) GIMs present significantly positive deviations compared to the Jason VTEC and GPS dSTEC. Technical University of Catalonia (UPC) rapid GIM UQRG exhibits the best performance in both Jason VTEC and GPS dSTEC analysis. The CAS GIMs show comparable performance with the results of the first four IAACs of the IGS. As expected, the poor performance of all GIMs is in equatorial regions and the high latitudes of the southern hemisphere. The consideration of generating multi-layer or three-dimensional ionospheric maps is emphasized to mitigate the inadequacy of ionospheric single-layer assumption in the presence of pronounced latitudinal gradients. The use of ionospheric observations from the new GNSS constellations and other space- or ground-based observation techniques is also suggested in the generation of future GIMs, given the sparse GPS/GLONASS stations in the southern hemisphere.

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