Electron Content Values Research Articles

Artificial Intelligence for Earthquake Prediction: A Preliminary System Based on Periodically Trained Neural Networks Using Ionospheric Anomalies

There is increasing evidence that anomalies in the ionosphere could appear a few days before large earthquakes. Many significant successes with using anomalies for predictions have been reported, although they are usually limited, both in space, to a specific geographic area, and in time, to one or a few events. To date, no solution has been presented that consistently yields the location and magnitude of future earthquakes and thus can be used to develop a warning service. The purpose of this research is to improve on the possible use of Global Ionospheric Maps for earthquake prediction. The use of three-dimensional data matrices, having spatiotemporal information to feed a convolutional neural network, is proposed in this contribution. This network was trained on all large earthquakes occurring from the beginning of the year 2011 to the beginning of October 2024 but it is proposed that it be periodically retrained with new data. This network has reached an accuracy of around 60% in the validation data for a division into eight categories of different earthquake magnitudes. Nevertheless, this percentage increases considerably if the classification into neighboring categories is also accepted, something that could be clearly admissible for the purposes of a warning system. The author believes that success in this endeavor has to come from a collaborative effort. For this reason, the training and validation data with three-dimensional matrices (latitude/longitude/time) of total electron content values along with the subsequent earthquake magnitudes are provided in this paper along with the trained network. Researchers are strongly encouraged to improve on the current neural network with or without the inclusion of additional information.

Reconstruction of ionospheric VTEC using empirical orthogonal function and its performance during extreme geomagnetic storm

This paper demonstrates that the spatial distribution of the ionospheric TEC over the Indian region can be reconstructed with appreciable accuracy using minimal numbers of empirical orthogonal functions as a basis. These basis functions were derived using the Singular Value Decomposition of a matrix composed of pragmatic vertical Total Electron Content (VTEC) values collected across varied ionospheric conditions and measured over the region of interest. The reconstruction was achieved by linearly combining the appropriately chosen significant bases with corresponding weight factors. The reconstruction accuracy of the algorithm was found to be better than 4 TECU (TECU = 1016 electrons/m2) for more than 99.9 % of the time when tested over the complete year of 2016 with only eight basis vectors. The containment factor, defined here, indicates the goodness of the chosen bases in representing the arbitrary VTEC distributions and is found to remain typically high, aiding in improved algorithm performance. The performance, however, was found to be sensitive to the seasons and geomagnetic conditions. Deteriorated performance was observed when tested for the St. Patrick's Day storm data. The deterioration was attributed to the structural alteration of the ionospheric plasma density and the presence of atypical modes during the storm. The results ascertain the prospect of a faithful representation of the spatial distribution of the ionospheric VTEC using limited parametric variables, which may find utility in navigation, radar, and various other applications.

Ionospheric responses to the tropical cyclones from different oceanic basins over the globe

The perturbations in the ionosphere due to eight tropical cyclones (TCs), namely Iota, Haima, Harold, Willa, Amphan, Gaja, Vadrah and Bulbul, originated and grown in different oceanic basins, are investigated. Total Electron Content (TEC) data, from Global Positioning System (GPS) TEC receiver in operation at Agartala (AGT) or different International GNSS Service (IGS) stations near the cyclone landfall regions, are used in this study. Despite some differences, the ionosphere responds to all tropical cyclones in an almost similar manner. Though the geomagnetic conditions are quiet and there are no perturbations due to any other geophysical phenomena in the active cyclonic storm stage, in all the cases there is a fall in average vertical total electron content (VTEC) deviations below the monthly mean value either on the landfall day or on the following day or even on just previous day. Decrements in Vertical Total Electron Content are found higher for tropical cyclones over North Indian and South Pacific oceanic basins. Recoveries in vertical total electron content values are slower for cyclones over the North Atlantic and North West Pacific basins. Recoveries in vertical total electron content (VTEC) values are slow for tropical cyclones (TCs) over the North Atlantic and North West Pacific basins. But those over other basins are quick. The longer the track of a tropical cyclone (TC), the higher is the reduction in the vertical total electron content (VTEC) value. A negative correlation exists between the maximum sustained surface wind velocities and the total periods of different TCs and also the difference of lowest average differential VTECs with that on the previous day. The observed anomaly in ionospheric responses might be due to the combined effect of TC-inspired gravity waves, ejection of neutral particles from the terminator of a tropical cyclone (TC) and lightning electric fields. To explain the observed results convective activities during TC, with the help of outgoing long wave radiation (OLR) map, are also taken into account. This study provides the primary results regarding regional characteristics and hence a comparative idea for the responses of the ionosphere to different tropical cyclones (TCs) from different geographical positions on the globe, which needs further comprehensive investigation in future.

Characteristic analysis of the differences between total electron content (TEC) values in global ionosphere map (GIM) grids

Abstract. Using total electron content (TEC) from a global ionosphere map (GIM) for ionospheric delay correction is a common method of eliminating ionospheric errors in satellite navigation and positioning. On this basis, the TEC of a puncture point can be obtained by GIM grid TEC interpolation. However, in terms of grid, only few studies have analyzed the TEC value size characteristics of its four grid points, that is, the TEC difference characteristics among them. In view of this, by utilizing the GIM data from high solar-activity years (2014) and low solar-activity years (2021) provided by CODE (Center for Orbit Determination in Europe), this paper proposes the grid TEC difference as a way of analyzing TEC variation characteristics within the grid, which is conducive to exploring and analyzing the variation characteristics of the ionosphere TEC in the single-station area. The value is larger in high solar-activity years and generally small in low solar-activity years, and the value of high-latitude areas is always smaller than that of low-latitude areas. Specifically, in high solar-activity years, most of the GIM grid TEC internal differences are within 4 TECu (1 TECu = 1016 electrons m−2) in high-latitude and midlatitude regions, while only 78.17 % are in low-latitude regions. In low solar-activity years, the TEC difference values within a GIM grid are mostly less than 2 TECu, and most of them in the high and middle latitudes are within 1 TECu. The main finding of this analysis is that the grid TEC differences are small for most GIM grids, especially in the midlatitudes to high latitudes of low solar years. This means that relevant extraction methods and processes can be simplified when TEC within these GIM grids is needed.

25-26 Ağustos 2018 Jeomanyetik Fırtına Sırasında Afrika Bölgesi Üzerindeki Manyetik Eşlenik Çiftleri Üzerindeki TEC Değişikliklerinin İncelenmesi

In this study, the electron transport process resulting from electromagnetic drift between two magnetic conjugate pairs over the African region during the August 25-26 2018 geomagnetic storm was investigated. The effects of geomagnetic conditions presented with Dst index and IMF Bz values on Total Electron Content (TEC) values at conjugate stations were compared separately for stormy and quiet periods. During the storm period, the effect of TEC values at stations in the northern hemisphere (Haifa and Djibouti) on the TEC values at stations in the southern hemisphere (Ambalavao and Malindi) is greater than the effect of TEC values in the southern hemisphere on TEC values in the northern hemisphere. According to this result, it can be said that the south-directed electromagnetic convection was more than the north-directed convection in the examined dates. When the coefficients are examined, it can be said that the interaction is more in the magnetic conjugate pair that is closer to the equator during the storm period, and the interaction is more in the magnetic conjugate pair that is far from the equator during the silent period. Considering the coefficients calculated for Dst and IMF Bz, it is seen that the TEC values are very small compared to their coefficients. From this it can be concluded that the effect of Dst and IMF Bz is much smaller than the effect of TEC values at a station on TEC values at its magnetic conjugates.

Ionospheric response and the impact on GPS positioning accuracy during the Tonga volcano eruption on 15 January 2022

The characteristics of ionospheric disturbances and GPS positioning accuracy during the eruption of the Hunga Tonga-Hunga Ha'apai (Abbreviated as 'Tonga' in this paper) on January 15, 2022 are investigated using International GNSS Service (IGS) and Swarm data. Firstly, the comparison of ionospheric responses between on January 15, 2022 and November 5, 2021 is conducted. The result shows that the number of the rate of TEC index (ROTI) values more than 0.5 TECU/min during Tonga Volcano eruption was significantly larger under the same moderate geomagnetic storms. Moreover, the values of Detrend Vertical Total Electron Content (DVTEC) above IGS stations were increased to 0.3–1 TECU on January 15, 2022. An interesting finding is shown that there was a linear corrleation between the DVTEC increment and the distance from the stations to Tonga Volcano. On the contrary, the DVTEC values on November 5, 2021 were all less than 0.1. Secondly, GPS positioning accuracy on January 15, 2022 and November 5, 2021 is analyzed, respectively. The GPS positioning accuracy was declined on January 15, 2022. Even, the GPS positioning errors of some stations were larger than 3 m. By comparision, the GPS positioning errors of the studied IGS stations on November 5, 2021 were all less than 0.2 m. The above comparison result indicates that the Tonga Volcano eruption on January 15, 2022 could affect the GPS positioning accuracy. At the same time, the GPS cycle slips of the studied IGS stations are obviously enhanced during the Tonga Volcano eruption. Finally, the interaction mechanism between the Tonga volcano eruption, ionospheric disturbances and GPS positioning accuracy is discussed and explored.

Airglow observed by a full-band imager together with multi-instruments in Taiwan during nighttime of 1 November 2021

This study demonstrates an innovative approach of using a full-band chromatic all-sky imager, routinely operational for monitoring sky conditions at Lulin observatory (23.5°N, 120.9°E, 12.5° N magnetic latitude), Taiwan, to investigate equatorial plasma bubbles (EPBs). Distinct north–south aligned EPB depletions are identified by decomposing the color-scale images to respective red (centered at 630 nm) and green (520 nm) channels, where blue channel (470 nm) helps for background suppression. The intense EPBs, drifting eastwards at 60–100 m/s velocity, are also associated with reduced total electron content (TEC) values; increased ROTI (rate of TEC index); remarkable range spread-F; and prominent fluctuations in Doppler frequency shifts as well as FORMOSAT-7/COSMIC-2 electron density/S4 scintillation profiles. The results show that a full-band chromatic imager offers a cost-effective alternative to investigate the EPBs usually detected in OI 630.0 and 557.7 nm airglow emissions.

Effects of ionosphere dispersion on wideband GNSS signals

Wideband GNSS signals suffer signal distortions such as waveform deformations and correlation peak reduction when traverse the ionosphere. Basing on the standard model of the ionosphere, we first demonstrate a modified ionosphere model to capture the ionosphere dispersion effects on wideband signals. We decompose the first-order ionosphere model into Taylor series. By using the first three terms of Taylor series, it is possible to account for all frequency components of wideband signals rather than treating them as single tone. We then make an analysis of the ionosphere dispersion effects on wideband GNSS signal tracking. It is revealed that the ionosphere dispersion degrades correlation peak results and shifts carrier-phase in the phase locked loop (PLL) output but dose not cause an additional delay for code measurements. Furthermore, we carry out a simulation for evaluating the ionosphere dispersion effects on tracking of various new generation wideband GNSS signals such as Galileo E5 AltBOC(15, 10) signals and BDS B3 BOC(15, 2.5) signals during ionosphere quietness and activities. The results show that the wider the bandwidth and the greater the total electron content (TEC) values, the more dramatic the ionosphere effects are. The Galileo E5 AltBOC(15, 10) signals are most affected among various wideband GNSS signals. For AltBOC(15, 10) signal tracking the correlation power loss is around 0.1 dB and the carrier-phase change is about 20° caused by the dispersion in quiet ionosphere case, and increases up to 0.35 dB and 33° during ionosphere activities, respectively.

Investigation of the planar midlatitude ionospheric trend under different levels of solar activity

A better understanding of the ionosphere through accurate mathematical models is no doubt a crucial element. This study focuses on the challenging problem of building a model representing the complex structure of the midlatitude ionosphere. Previous studies have shown that a regional planar model is suitable in representing the total electron content (TEC) trend in the midlatitude ionosphere in both hemispheres. In this study, the planar trend model for 12 non-overlapping northern hemisphere regions in three groups of geographically near 4 regions is further investigated under different levels of solar activity; low, moderate and high. To that end, the coefficients of the model are estimated in the least squares sense using total electron content values from global ionospheric maps (GIMs) for the years 2009, 2012 and 2014. Subsequently, these coefficients are used to reconstruct estimated TEC maps which are then compared with actual GIM-TEC by investigating their difference in normalized L2 norm squared sense. The regional planar trend model provides a particularly successful representation in the years 2012 and 2014 for which the solar activity level is the dominant factor determining the TEC trend. Under low solar activity conditions of 2009, other factors such as ocean currents, temperature variations and meteorological phenomena are suspected to have a considerable effect in some regions depending on their geographic location and on seasonal trends in those regions. As an example, studies show that under the influence of the Pacific Decadal Oscillation (PDO) and Siberian High (SH), a significant cooling trend between 2004 and 2018 in autumn is observed in Eurasia, which, in conjunction with the low solar activity levels, may be related to the deviations from the actual GIM-TEC in 2009 in these regions. As solar radiation increases, however, such bottom-side forcings are masked in 2012 and 2014 and these deviations are no longer observed.

Effects of 15th January 2010 Annular Solar Eclipse on Traveling Ionospheric Disturbances and Equatorial Plasma Bubbles over Low Latitude Regions of East Africa

The influence of the 15th January 2010 annular solar eclipse on traveling ionospheric disturbances (TIDs) and equatorial plasma bubbles (EPBs) is studied using data from six global navigation and satellite system (GNSS) receivers spread across the path of annularity over the low latitude region of East Africa. The GNSS receivers are stationed at Nairobi (RCMN), Malindi (MAL2), and Eldoret (MOIU) in Kenya; Mbarara (MBAR) in Uganda; Kigali (NURK) in Rwanda; and Mtwara (MTWA) in Tanzania. The study period ranges from 12th to 18th January 2010, three days before and after the 15th January 2010 annular solar eclipse. The year 2010 marked the beginning phase of solar cycle 24, evidently observed in low total electron content (TEC) values and the disturbed storm time index (Dst). The eclipse started at 7 : 06 LT and ended at 10 : 14 LT, with MOIU and RCMN experiencing eclipse magnitudes of 0.946 and 0.93, respectively. The maximum obscuration occurred between 8 : 21 LT and 8 : 34 LT across most of the stations. A detrending on vertical TEC (VTEC) derived from GNSS receivers across or close to the path of totality revealed a reduction of ∼2-3 TECU during the maximum phase of the eclipse. The level of reduction was highly close to the totality path and decreased smoothly away from the totality path. Using a background polynomial fitting technique on diurnal TEC, we analyzed TIDs along NURK-MBAR-MOIU and MOIU-RCMN-MAL2 GPS arrays. The results revealed a wavelike perturbation with a virtual horizontal velocity of 830m/s and ∼1 TECU amplitude propagating eastward along the MOIU-RCMN-MAL2 GPS array. The study reports a moderate scintillation activity of 0.5 ≤ ROTI ≤ 0.9 values, demonstrating the presence of few EPBs over the region. The results show a latitudinal variation in GPS-TEC scintillation activities and suggest a possible influence of the eclipse on the observed increase in average scintillation levels across East Africa.

Negative VTEC with spherical harmonic expansion model under different solar activity conditions

The Earth’s ionosphere can be described by a spherical harmonic (SH) expansion up to a specific degree. However, there exist negative vertical total electron content (VTEC) values in the global ionosphere map (GIM) with the SH expansion model. In this contribution, we specifically investigated the negative VTEC values that are induced by the SH expansion model and validated the performance of the inequality-constrained least squares (ICLS) method in eliminating the negative VTEC values. The GPS data from 2004 to 2017 was selected to cover one solar cycle and the experiments under different solar activity conditions were analyzed. The results in our work show that the occurrence of the negative VTEC values is attributed to the deficiency of the SH expansion model when the VTEC itself is small instead of the unevenly distribution of the GNSS stations. The negative VTEC values appear periodically in the temporal domain, showing apparently one year and half year periods. During one year, two peaks in June and December can be observed in the time series of the negative VTEC values. The number of negative VTEC values in June is obvious larger than that in December. During one solar cycle, the number of negative VTEC values under quiet solar activity condition is obvious larger than that under strong solar activity condition. In the spatial domain, the appearance of the negative VTEC values is strongly related with the movement of the subsolar point. In the latitude of the subsolar point has the largest magnitude, the negative values will appear on the opposite hemisphere and the further from the subsolar point the more negative values. The maximum number of the negative VTEC values in the southern hemisphere appears in June, while the peak value in the northern hemisphere appears in December. The maximum number of negative VTEC values in the southern hemisphere is generally larger than that in the northern hemisphere. In addition, the negative VTEC values are distributed both at middle latitude and high latitude in the southern hemisphere, while they are mainly distributed at high latitude in the northern hemisphere. When the ICLS method is used, the negative VTEC values can be eliminated efficiently and it has nearly no influence on the positive VTEC values. The ICLS method can also improve the receiver’s differential code bias (DCB) and significantly decrease the unreasonable negative slant TEC (STEC) values along the lines of sight. Using the final GIM product of the Jet Propulsion Laboratory (JPLG) as a reference, the root mean square (RMS) of the ICLS solution shows maximum 25%, 20% and 45% improvement relative to the least squares (LS) solution at northern high latitude, southern middle latitude and southern high latitude, respectively.

Investigation on Horizontal and Vertical Traveling Ionospheric Disturbances Propagation in Global‐Scale Using GNSS and Multi‐LEO Satellites

AbstractGlobal Navigation Satellite System (GNSS) observations from worldwide ground‐based stations have been extensively used in traveling ionospheric disturbance (TID) detections. However, these observations primarily cover land area, thus causing a challenging problem of interpreting the global propagating characteristics of large‐scale TIDs (LSTIDs), especially over the ocean area. Meanwhile, Total Electron Content (TEC) values derived from ground‐based GNSS signals propagating through the whole ionosphere have an integral character, and we were unable to obtain the propagation and dissipation of TIDs in the vertical direction using solely ground‐based GNSS TEC data. In this study, apart from ground‐based GNSS observations, in situ data and GNSS observations from precise orbit determination receivers on board Low‐Earth‐Orbit (LEO) satellites were integrated for the first time for the global large‐scale TID investigation during the St. Patrick's Day geomagnetic storm. Through experiments, we found that LEO satellite observations effectively compensate for areas where the TIDs cannot be detected by sparse ground‐based GNSS data, particularly over the ocean and polar areas. The space‐borne TEC and in situ data provided the new observational evidences of LSTIDs propagating up to the topside ionosphere during the 17 March 2015 storm, serving as great supplements to ground‐based GNSS data. Combining space‐borne GNSS data with in situ data at various orbit altitudes offers opportunities for theoretical studies of TID propagations at different ionospheric heights and for a better understanding of the complex coupled processes of the TIDs with the geospace environment.

Jupiter's Enigmatic Ionosphere: Electron Density Profiles From the Pioneer, Voyager, and Galileo Radio Occultation Experiments

AbstractRadio occultation experiments on the Pioneer and Voyager missions obtained the first seven electron density profiles Ne(h) of Jupiter's ionosphere. We use the five complete Ne(h) observations to assess patterns and processes linked to photo‐chemical‐equilibrium (PCE) theory, modeled previously to be the domain below ∼1,000 km. We find that the Ne(h) profiles are highly structured and identification of the maximum electron density and its height do not follow PCE expectations for layers produced by the Sun's soft X‐rays and extreme ultraviolet. Pre‐dawn profiles often show larger electron densities than dusk‐side profiles, inconsistent with simple chemical decay throughout nighttime. We examined total electron content (TEC) values, defined as Ne(h) integrated up to a 3,500 km height, and found statistically significant TEC correlations (correlation coefficient ∼0.85) with solar fluxes over solar cycle time scales. The subsequent set of 25 Ne(h) profiles obtained during the Galileo mission confirmed all of the variability patterns found by Pioneer and Voyager. Most notable was a weaker solar cycle pattern for TEC. Yet, different solar cycle characteristics during the three missions cannot explain their different values for TEC. Average Ne(h) profiles from the early missions (P10‐11; V1‐2) revealed a three‐layer system that was confirmed by average Galileo results. Models using faster electron‐ion recombination caused by vibrationally excited H2 converting atomic ions to molecular ions could lead to enhanced removal of plasma near ∼1,000 km, and thus the topside layer formation that often appears at ∼1,500 km, while XUV radiation likely produces the two lower layers in the PCE domain.

Discussing Total Electron Content over the Solar Wind Parameters

Modeling and forecasting of Total Electron Content (TEC) values by an Artificial Neural Network model (ANNm) have high agreement on November 2003, 2004 superstorms. The work discusses Solar Wind Parameters (SWp) from OMNI (Operating Missions as a Node on the Internet) and TEC (TECU) data (International Reference Ionosphere) IRI-2012, IRI-2016 on November 20, 2003 (Dst = –422 nT) and on November 08, 2004 (Dst = –374 nT) Geomagnetic Storms (GSs). The paper commences with a 120-hour GS exhibition of SWp and proceeds with the correlation data of the variables, their hierarchical tracks, and inner dispersions. The ANNm with SWp as the input and TEC data as the output are introduced. The performance of the ANNm for 2003 and 2004 superstorms is adequate. The Correlation Coefficient (R) and Root Mean Square Error (RMSE) of the ANNm are 97.5%, 1.17 TECU (IRI-2012), and 97.9%, 1.09 TECU (IRI-2016) for the 2003 GS and 97.0%, 0.89 TECU (IRI-2012), and 98.0%, 1.61 TECU (IRI-2016) for 2004 GS. Parameters effect of the R constant of TEC data points out to the dynamic pressure (nPa), the magnetic field Bz component (nT), the flow speed (km/s), and the proton density (1/cm3). Besides, the absolute total error and the variance of the predicted TEC data for November 2003 and November 2004 GSs are 0.06 (0.30%) with 0.013 variance (IRI-2012), 0.09 (0.49%) with 0.016 variance (IRI-2016) for 2003 storm and 0.13 (0.73%) with 0.033 variance (IRI-2012), and 0.11 (1.06%) with 0.035 variance (IRI-2016) for 2004. It means that the paper models TEC data with considerable consistency over the SWp.

Performance of NeQuick-2 and IRI-Plas 2017 Models during Solar Maximum Years in 2013–2014 over Equatorial and Low Latitude Regions

This paper carries out a comparative investigation of the Total Electron Content (TEC) values calculated by using the NeQuick-2 and IRI-Plas 2017 models. The investigation was carried out for the solar maximum year of 2013–2014 with data from eight GPS stations within the equatorial and low latitude regions. The results show that both models agree quite well with the observed TEC values obtained from GPS measurements in all the stations, although with some overestimations and underestimations observed during the daytime and nighttime hours. The NeQuick-2 model, in general, performed better in months, seasons, and in most of the stations when the IRI-Plas overestimates the GPS-TEC. However, it is interesting to know that with an increase in solar activity in some seasons, the quality of forecasting IRI-Plas can improve, whereas for the NeQuick-2 model, it decreases, but this is not true for all the seasons and all the stations. Factors causing the discrepancies in the IRI-Plas data model might be caused by the plasmaspheric part included in the IRI, and it is found to be maximum at the MBAR (34%) station, whereas that of the NeQuick-2 data model is found to be maximum at the ADIS (47.7%) station. There is a latitudinal dependence for both models in which the prediction error decreases with the increasing latitudes.

Study the Relationship of Earthquake and Ionosphere Using IRI TEC for Education

This research is aimed to study and analyze the relationship between the earthquake events and the disturbance of ionosphere. The method is by using the International Reference Ionosphere (IRI) model to get Total Electron Content (TEC) values and then find the correlation on earthquake events and ionosphere. The result is to be correlated at 0.056, which shows the evidence of correlationon earthquake events and ionosphere. For the future work, we will study the significant on the development of earthquake warning system. This study can be used for educational purposes.

Spatial and Temporal Distributions of Ionospheric Irregularities Derived from Regional and Global ROTI Maps

Major advancements in the monitoring of both the occurrence and impacts of space weather can be made by evaluating the occurrence and distribution of ionospheric disturbances. Previous studies have shown that the fluctuations in total electron content (TEC) values estimated from Global Navigation Satellite System (GNSS) observations clearly exhibit the intensity levels of ionospheric irregularities, which vary continuously in both time and space. The duration and intensity of perturbations depend on the geographic location. They are also dependent on the physical activities of the Sun, the Earth’s magnetic activities, as well as the process of transferring energy from the Sun to the Earth. The aim of this study is to establish ionospheric irregularity maps using ROTI (rate of TEC index) values derived from conventional dual-frequency GNSS measurements (30-s interval). The research areas are located in Southeast Asia (15°S–25°N latitude and 95°E–115°E longitude), which is heavily affected by ionospheric scintillations, as well as in other regions around the globe. The regional ROTI map of Southeast Asia clearly indicates that ionospheric disturbances in this region are dominantly concentrated around the two equatorial ionization anomaly (EIA) crests, occurring mainly during the evening hours. Meanwhile, the global ROTI maps reveal the spatial and temporal distributions of ionospheric scintillations. Within the equatorial region, South America is the most vulnerable area (22.6% of total irregularities), followed by West Africa (8.2%), Southeast Asia (4.7%), East Africa (4.1%), the Pacific (3.8%), and South Asia (2.3%). The generated maps show that the scintillation occurrence is low in the mid-latitude areas during the last solar cycle. In the polar regions, ionospheric irregularities occur at any time of the day. To compare ionospheric disturbances between regions, the Earth is divided into ten sectors and their irregularity coefficients are calculated accordingly. The quantification of the degrees of disturbance reveals that about 58 times more ionospheric irregularities are observed in South America than in the southern mid-latitudes (least affected region). The irregularity coefficients in order from largest to smallest are as follows: South America, 3.49; the Arctic, 1.94; West Africa, 1.77; Southeast Asia, 1.27; South Asia, 1.24; the Antarctic, 1.10; East Africa, 0.89; the Pacific, 0.32; northern mid-latitudes, 0.15; southern mid-latitudes, 0.06.

Three-dimensional Tomography of Coseismic Ionospheric Disturbances from the 2016 West Sumatera Earthquake

Global Navigation Satellite System (GNSS) is a navigation system that uses satellite signals to determine its position, which consists of several satellites arranged in a constellation system. GNSS transmits signals to receivers on Earth. The GNSS receiver determines the user’s position, speed, and time by processing the signals transmitted by the satellites. The initial purpose of launching the GNSS was for navigation purposes, but along with its development, GNSS can be used for the purposes of observing deformation of the earth’s crust and in studying the atmosphere. The delayed wave data when passing through the ionosphere can be used to obtain Total Electron Content (TEC) values which then used to study ionospheric disturbances. Ionospheric disturbances are caused by various phenomena, the most common one is the ionospheric disturbances caused by the induction of acoustic and gravitational waves excited by co seismic crustal motions from large earthquakes. Ionospheric disturbances that happened before an earthquake are called Pre-seismic Ionospheric Disturbances and those that occur after an earthquake are called Co-seismic Ionospheric Disturbances (CID). Most studies of ionospheric disturbances still provide information on the timing and value of TEC anomalies in 2D form. Therefore, in this study, a 3D ionosphere profile modelling using computed 3D tomography will be carried out. The 3D information provided is in the form of time, ionosphere altitude and TEC anomaly value by utilizing GNSS data. The TEC anomaly value is obtained from the calculation of linear combination of the ionosphere. This study aims to obtain a spatial and temporal analysis of the CID caused by the West Sumatra Earthquake on March 2, 2016.

On Use of Low Cost, Compact GNSS Receiver Modules for Ionosphere Monitoring

AbstractGeodetic or special purpose Global Navigation Satellite System (GNSS) receivers are used for ionosphere monitoring and research. Dual frequency, compact, low‐cost commercial GNSS modules can provide raw GNSS data and are commonly used for positioning applications. This paper presents the applicability of these compact modules for monitoring ionospheric activities. A comparative study between Javad Triumph LS, a costly geodetic receiver, and an Ublox ZED‐F9P, a low‐cost, dual‐frequency, compact module is carried out to explore the potential of the low‐cost devices for ionosphere probing. Studies are carried out on signal strength values (C/N0) and vertical total electron content (VTEC) values. From the concurrently collected GPS data, a bias of 2.2–4.9 dBHz in signal strength values are observed between the two types of receivers depending on the signal frequency band. The VTEC values calculated from the Ublox module are in close agreement with the values obtained from the Triumph LS receiver. Therefore, the compact module shows the potential for use in ionosphere monitoring with clear advantages in cost, size, and power consumption. However, the signal strength values obtained from such compact modules need to be calibrated using standard GNSS receivers. A GNSS‐based Ionosphere Monitoring Unit (GIMU) is also proposed in this manuscript by the integration of a compact, low‐cost GNSS module with a single‐board computer and a wireless data communication module. Real‐time, cost‐effective, concurrent ionosphere monitoring over a geographically distributed network is possible using a network of such units.

Validating the impact of various ionosphere correction on mid to long baselines and point positioning using GPS dual-frequency receivers

Abstract Due to the ionosphere delay, which has become the dominant GPS error source, it is crucial to remove the ionospheric effect before estimating point coordinates. Therefore, different agencies started to generate daily Global Ionosphere Maps (GIMs); the Vertical Total Electron Content (VTEC) values represented in GIMs produced by several providers can be used to remove the ionosphere error from observations. In this research, an analysis will be carried with three sources for VTEC maps produced by the Center for Orbit Determination in Europe (CODE), Regional TEC Mapping (RTM), and the International Reference Ionosphere (IRI). The evaluation is focused on the effects of a specific ionosphere GIM correction on the precise point positioning (PPP) solutions. Two networks were considered. The first network consists of seven Global Navigation Satellite Systems (GNSS) receivers from (IGS) global stations. The selected test days are six days, three of them quiet, and three other days are stormy to check the influence of geomagnetic storms on relative kinematic positioning solutions. The second network is a regional network in Egypt. The results show that the calculated coordinates using the three VTEC map sources are far from each other on stormy days rather than on quiet days. Also, the standard deviation values are large on stormy days compared to those on quiet days. Using CODE and RTM IONEX file produces the most precise coordinates after that the values of IRI. The elimination of ionospheric biases over the estimated lengths of many baselines up to 1000 km has resulted in positive findings, which show the feasibility of the suggested assessment procedure.