scholarly journals Wave Signatures in Total Electron Content Variations: Filtering Problems

2020 ◽  
Vol 12 (8) ◽  
pp. 1340 ◽  
Author(s):  
Boris Maletckii ◽  
Yury Yasyukevich ◽  
Artem Vesnin
Keyword(s):  
Total Electron Content ◽  
Moving Average ◽  
Global Navigation Satellite Systems ◽  
Analytical Models ◽  
Mean Bias Error ◽  
Bias Error ◽  
Electron Content ◽  
Type I ◽  
Total Electron ◽  
Order Polynomial

Over recent years, global navigation satellite systems (GNSSs) have been increasingly used to study near-Earth space. The basis for such studies is the total electron content (TEC) data. Standard procedures for detecting TEC wave signatures include variation selection and detrending. Our experience showed that the inaccurate procedure causes artifacts in datasets which might affect data interpretation, particularly in automated processing. We analyzed the features of various detrending and variation selection methods. We split the problem of the GNSS data filtering into two subproblems: detrending and variation selection. We examined centered moving average, centered moving median, 6th-order polynomial, Hodrick–Prescott filter, L1 filter, cubic smoothing spline, double-applied moving average for the GNSS-TEC detrending problem, and centered moving average, centered moving median, Butterworth filter, type I Chebyshev filter for the GNSS-TEC variation selection problem in this paper. We carried out the analysis based on both model and experimental data. Modeling was based on simple analytical models as well as the International Reference Ionosphere. Analysis of TEC variations of 2–10 min, 10–20 min, and 20–60 min under insufficient detrending conditions showed that the higher errors appear for the longer periods (20–60 min). For the detrending problem, the smoothing cubic spline provided the best results among the algorithms discussed in this paper. The spline detrending featured the minimal value of the mean bias error (MBE) and the root-mean-square error (RMSE), as well as high correlation coefficient. The 6th-order polynomial also produced good results. Spline detrending does not introduce a RMSE more than 0.25 TECU and MBE > 0.35 TECU for IRI trends, while, for the 6th-order polynomial, these errors can exceed 1 TECU in some cases. However, in 95% of observations the RMSE and MBE do not exceed 0.05 TECU. For the variation selection, the centered moving average filter showed the best performance among the algorithms discussed in this paper.

scholarly journals Ionospheric Response to the Space Weather Events of 4-10 September 2017: First Chilean Observations

2019 ◽  
Vol 13 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Manuel Bravo ◽  
Carlos Villalobos ◽  
Rodrigo Leiva ◽  
Luis Tamblay ◽  
Pedro Vega-Jorquera ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Space Weather ◽  
Global Navigation Satellite Systems ◽  
Time Interval ◽  
Electron Content ◽  
Dual Frequency ◽  
Field Station ◽  
Total Electron ◽  
Satellite Systems ◽  
Weather Events

Objective: The diurnal variations of several ionospheric characteristics during the Space Weather Events of 4-10 September 2017, for Chilean latitudes, will be reported. Materials and Methods: Observations were made using a recently installed ionosonde at the Universidad de La Serena field station (29°52'S; 71°15’W). Also, reported is the total electron content determined using the upgraded Chilean network of dual-frequency Global Navigation Satellite Systems (GNSS) receivers. Results: Sudden ionospheric disturbances are described in terms of the minimum reflection frequency determined from ionosonde records. An attempt to derive the extent of the effect on high frequency propagation paths in the region is made using simultaneous ionosonde observations at other locations. The geomagnetic storm ionospheric effects are discussed in detail using the observed diurnal variation of maximum electron concentration (NmF2), virtual height of the F-region (h’F/F2) and Total Electron Content (TEC). These are complemented with the time-latitude variation of TEC for the 70°W meridian. Conclusion: It is found that large increases of NmF2, h’F/F2 and TEC observed during 8 September 2017 storm are well described in terms of the evolution of the Equatorial Ionospheric Anomaly (EIA) over the same time interval. Known physical mechanisms are suggested to explain most of the observations.

Total Electron Content and Seismic Ambient Noise analysis prior to significant earthquakes

2020 ◽  
Author(s):  
Sabyasachi Sahu ◽  
Kajaljyoti Borah ◽  
Prashant Kumar Champati ray
Keyword(s):  
Total Electron Content ◽  
Ambient Noise ◽  
Seismic Velocity ◽  
Noise Analysis ◽  
Global Navigation Satellite Systems ◽  
Electron Content ◽  
Total Electron ◽  
Seismic Ambient Noise ◽  
Seismic Velocity Changes ◽  
Velocity Changes

<p>The seismo-ionospheric interaction study with respect to earthquake events using Total Electron Content (TEC) data derived from Global Navigation Satellite Systems (GNSS) receivers can be used to detect pre-earthquake ionospheric anomalies. This is primarily because ionospheric anomaly variation has been emerged as one of the most promising precursors. In recent times, many studies have reported pre-seismic ionospheric anomalies of TEC prior to major earthquakes. However, the results are not uniform and therefore, considerable amount of data processing and validation is required before this can be used in operational mode.  To ensure the seismogenic cause of TEC variation, geomagnetic and solar-activities are also compared with TEC values prior to the earthquakes and our analysis has proved that TEC anomalies can be used as earthquake precursors. Several global events and Himalayan earthquakes have been studied and results are very encouraging for developing a methodology that can qualify for detection of early sign of earthquakes. It may be far from early warning system (EWS) with information on magnitude, location and time, but it is a significant achievement in the field of earthquake geology where no methodology exists on forewarning of seismic events.</p><p> Seismic velocity changes computed by applying modern techniques in seismic interferometry reveals that considerably large earthquakes can trigger a decline in seismic velocity prior to the mainshock. Cross-correlation of diffuse wave fields, including ambient seismic noise can provide the Green’s function between pair of receivers recording seismic activity. Using the known properties of the seismic ambient noise, recorded over a large period of time, seismic velocity changes before the earthquake has been observed which can act as a potential precursor. Decrease in the seismic velocity few days before the main event suggest that co-seismic damage begins to occur even before the mainshock, which could be a result of foreshocks. The main shock records the lowest relative seismic velocity change. The potential use of the ambient noise as an earthquake precursor can be concluded after rigorous analysis.</p>

Inter-hemispheric comparison of the ionosphere-plasmasphere system from multi-instrumental/model approach.

2020 ◽  
Author(s):  
Nicolas Bergeot ◽  
John Bosco Habarulema ◽  
Jean-Marie Chevalier ◽  
Tshimangadzo Matamba ◽  
Elisa Pinat ◽  
...  
Keyword(s):  
South African ◽  
Total Electron Content ◽  
Geomagnetic Storms ◽  
Global Navigation Satellite Systems ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Hemispheric Differences ◽  
Total Electron ◽  
Precise Knowledge

<p>An increasing demand for a better modelling and understanding of the Ionosphere-Plasmasphere system (I/Ps) is required for both scientific and public practical applications using electromagnetic wave signals reflecting on or passing through this layer. This is the case for the Global Navigation Satellite Systems (GNSS, i.e. GPS, GLONASS, Galileo) and for spacecraft designers and operators who need to have a precise knowledge of the electron density distribution.</p><p>Additionally, despite the long-term ionospheric studies that have been on-going for many decades, a number of aspects are still complicated to understand and forecast accurately even in mid-latitude regions during quiet conditions. Performing inter-hemispherical climatological studies in European and South African regions should highlight differences/similarities in I/Ps response during different phases of solar activity and geophysical conditions.</p><p>In that frame, the Royal Observatory of Belgium (ROB) and the South African National Space Agency (SANSA) started a collaboration named “Interhemispheric Comparison of the Ionosphere-Plasmasphere System” (BEZA-COM). The goal is to provide inter-hemispheric comparison of the I/Ps implying: (1) a characterization of the climatological behavior of the Total Electron Content (TEC) in the I/Ps, over European, South African, Arctic and Antarctica regions; (2) an identification of the mechanisms that regulate inter-hemispheric differences, asymmetries and commonalities in the I/Ps from low to high-latitudes, (3) study of the different responses of the I/Ps during extreme solar events and induced geomagnetic storms in the two hemispheres.</p><p>In this paper, we reprocessed the GNSS data (GPS+GLONASS) of the dense EUREF Permanent GNSS Network (EPN) and South African TRIGNET networks as well as IGS stations for the period 1998-2018. The output consists in vertical Total Electron Content (vTEC), estimated every 15 min., and covering the central European and South African regions. The vTEC is then extracted at two conjugated locations and used to constrain empirical models to highlight the climatological behavior of the ionospheric vTEC over Europe and South Africa. From the results, we will show that the differences are quite significant. To give first answers on these differences, we also compared these models with ionosondes long-term data based models (for foF2 and hmF2) at two conjugated locations (Grahamstown and Průhonice) as well as long-term NRLMSISE O/N<sub>2</sub> ratio.</p>

scholarly journals A Refinement Method of Real-Time Ionospheric Model for China

2020 ◽  
Vol 12 (20) ◽  
pp. 3354
Author(s):  
Yang Wang ◽  
Yibin Yao ◽  
Liang Zhang ◽  
Mingshan Fang
Keyword(s):  
Real Time ◽  
Total Electron Content ◽  
Global Navigation Satellite Systems ◽  
Single Frequency ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Ionospheric Model ◽  
Total Electron ◽  
Satellite Systems ◽  
Refinement Method

Ionospheric delay is a crucial error source and determines the source of single-frequency precise point positioning (SF-PPP) accuracy. To meet the demands of real-time SF-PPP (RT-SF-PPP), several international global navigation satellite systems (GNSS) service (IGS) analysis centers provide real-time global ionospheric vertical total electron content (VTEC) products. However, the accuracy distribution of VTEC products is nonuniform. Proposing a refinement method is a convenient means to obtain a more accuracy and consistent VTEC product. In this study, we proposed a refinement method of a real-time ionospheric VTEC model for China and carried out experiments to validate the model effectiveness. First, based on the refinement method and the Centre National d’Études Spatiales (CNES) VTEC products, three refined real-time global ionospheric models (RRTGIMs) with one, three, and six stations in China were built via GNSS observations. Second, the slant total electron content (STEC) and Jason-3 VTEC were used as references to evaluate VTEC accuracy. Third, RT-SF-PPP was used to evaluate the accuracy in the positioning domain. Results showed that even if using only one station to refine the global ionospheric model, the refined model achieved a better performance than CNES and the Center for Orbit Determination in Europe (CODE). The refinement model with six stations was found to be the best of the three refinement models.

Total electron content prediction using singular spectrum analysis and autoregressive moving average approach

2022 ◽  
Vol 367 (1) ◽  
Author(s):  
J. R. K. Kumar Dabbakuti ◽  
Mallika Yarrakula ◽  
Sampad Kumar Panda ◽  
Punyawi Jamjareegulgarn ◽  
Mohd Anul Haq
Keyword(s):  
Total Electron Content ◽  
Spectrum Analysis ◽  
Moving Average ◽  
Singular Spectrum Analysis ◽  
Autoregressive Moving Average ◽  
Electron Content ◽  
Total Electron ◽  
Singular Spectrum

scholarly journals Comparison of temporal fluctuations in the total electron content estimates from EISCAT and GPS along the same line of sight

2013 ◽  
Vol 31 (4) ◽  
pp. 745-753 ◽  
Author(s):  
B. Forte ◽  
N. D. Smith ◽  
C. N. Mitchell ◽  
F. Da Dalt ◽  
T. Panicciari ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Geographic Region ◽  
Global Navigation Satellite Systems ◽  
Line Of Sight ◽  
Electron Content ◽  
Long Distance ◽  
Total Electron ◽  
Temporal Fluctuations ◽  
The Impact ◽  
Eiscat Measurements

Abstract. The impact of space weather events on satellite-based technologies (e.g. satellite navigation and precise positioning) is typically quantified on the basis of the total electron content (TEC) and temporal fluctuations associated with it. GNSS (global navigation satellite systems) TEC measurements are integrated over a long distance and thus may include contributions from different regions of the ionised atmosphere which may prevent the resolution of the mechanisms ultimately responsible for given observations. The purpose of the experiment presented here was to compare TEC estimates from EISCAT and GPS measurements. The EISCAT measurements were obtained along the same line of sight of a given GPS satellite observed from Tromsø. The present analyses focussed on the comparison of temporal fluctuations in the TEC between aligned GPS and EISCAT measurements. A reasonably good agreement was found between temporal fluctuations in TEC observed by EISCAT and those observed by a co-located GPS ionospheric monitor along the same line of sight, indicating a contribution from structures at E and F altitudes mainly to the total TEC in the presence of ionisation enhancements possibly caused by particle precipitation in the nighttime sector. The experiment suggests the great potential in the measurements to be performed by the future EISCAT_3D system, limited only in the localised geographic region to be covered.

scholarly journals Evaluating Total Electron Content (TEC) Detrending Techniques in Determining Ionospheric Disturbances during Lightning Events in A Low Latitude Region

2021 ◽  
Vol 13 (23) ◽  
pp. 4753
Author(s):  
Louis Osei-Poku ◽  
Long Tang ◽  
Wu Chen ◽  
Chen Mingli
Keyword(s):  
Total Electron Content ◽  
Communication Systems ◽  
Time Window ◽  
Ionospheric Disturbance ◽  
Time Frame ◽  
Global Navigation Satellite Systems ◽  
Electron Content ◽  
Total Electron ◽  
Satellite Systems ◽  
The Impact

Total Electron Content (TEC) from Global Navigation Satellite Systems (GNSS) is used to ascertain the impact of space weather events on navigation and communication systems. TEC is detrended by several methods to show this impact. Information from the detrended TEC may or may not necessarily represent a geophysical parameter. In this study, two commonly used detrending methods, Savitzky–Golay filter and polynomial fitting, are evaluated during thunderstorm events in Hong Kong. A two-step approach of detection and distinguishing is introduced alongside linear correlation in order to determine the best detrending model. Savitzky–Golay filter on order six and with a time window length of 120 min performed the best in detecting lightning events, and had the highest moderate positive correlation of 0.4. That the best time frame was 120 min suggests that the observed disturbances could be travelling ionospheric disturbance (TID), with lightning as the potential source.

scholarly journals Detection of ionospheric signatures from GPS-derived total electron content maps

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
T. Durgonics ◽  
G. Prates ◽  
M. Berrocoso
Keyword(s):  
Total Electron Content ◽  
Geographical Information Systems ◽  
Measurement Data ◽  
Early Warning Systems ◽  
Global Navigation Satellite Systems ◽  
Geographical Information ◽  
Electron Content ◽  
Total Electron ◽  
Lorca Earthquake ◽  
Satellite Systems

AbstractThe processing of measurement data from satellite constellations such as Global Navigation Satellite Systems (GNSS), including the well-known Global Positioning System (GPS), have been successfully applied to virtually all areas of geophysical sciences. In this work, a method is described where Geographical Information Systems (GIS) are employed to build hourly ionospheric Total Electron Content (TEC) maps for 2011 over the southern Iberian Peninsula. The maps used GPS-derived geometryfree linear combinations attained from station data from the Algarve, Alentejo (Portugal), Andalusia, Murcia and Valencia (Spain) regions. Following the construction of the ionospheric maps, it was possible to relate these results to natural phenomena. The observed phenomena included diurnal and seasonal variations: daytime TEC maxima, nighttime TEC peaks, summer TEC value decreases, and spring and fall TEC maxima. After validation of these periodic phenomena, detection of non-periodic changes, such as solar flares and tectonic interactions with the ionosphere were attempted. The results showed a TEC increase following a selected solar flare event and a potential TEC build-up prior to the 2011 Lorca earthquake. Further studies could open up the possibility of building early warning systems. The presented methods, based on available software packages, are also of value in monitoring the effect of the ionosphere on radio signals, satellite and mobile communication, power grids, and for accurate GNSS navigation.

scholarly journals Granger causality analysis of deviation in total electron content during geomagnetic storms in the equatorial region

2021 ◽  
Vol 68 (1) ◽  
pp. 1-25
Author(s):  
Sumitra Iyer ◽  
Alka Mahajan
Keyword(s):  
Granger Causality ◽  
Total Electron Content ◽  
Geomagnetic Storms ◽  
Spatial Scales ◽  
Equatorial Region ◽  
Global Navigation Satellite Systems ◽  
Electron Content ◽  
Causality Analysis ◽  
Total Electron ◽  
Satellite Systems

AbstractThe total electron content (TEC) in the ionosphere widely influences Global Navigation Satellite Systems (GNSS) especially for critical applications by inducing localized positional errors in the GNSS measurements. These errors can be mitigated by measuring TEC from stations located around the world at various temporal and spatial scales and using them for advanced forecasting of TEC. The TEC can be used as a tool in understanding space weather phenomena such as geomagnetic storms which cause disruptions in the ionosphere. This paper examines the causal relationship between perturbations in TEC caused by geomagnetic storms. The causality between two geomagnetic indices auroral electrojet (AE) and disturbed storm index (Dst) and TEC is investigated using Granger causality at two low-latitude stations, Bangalore and Hyderabad. The outcomes of this study strengthen the regional understanding and modeling of ionospheric parameters which can contribute towards the global efforts for modeling and reducing the ionospheric effects on trans-ionospheric communication and navigation. The causal inferences combined with the data-driven model can be useful in identifying the correct and informative physical quantities to improve the forecasting models.

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