Total Electron Content Measurements Research Articles

Three methods to retrieve slant total electron content measurements from ground‐based GPS receivers and performance assessment

AbstractThe high sampling rate along with the global coverage of ground‐based receivers makes Global Positioning System (GPS) data particularly ideal for sensing the Earth's ionosphere. Retrieval of slant total electron content measurements (TECMs) constitutes a key first step toward extracting various ionospheric parameters from GPS data. Within the ionospheric community, the interpretation of TECM is widely recognized as the slant total electron content along the satellite receiver line of sight, biased by satellite and receiver differential code biases (DCBs). The Carrier‐to‐Code Leveling (CCL) has long been used as a geometry‐free method for retrieving TECM, mainly because of its simplicity and effectiveness. In fact, however, the CCL has proven inaccurate as it may give rise to TECM very susceptible to so‐called leveling errors. With the goal of attaining more accurate TECM retrieval, we report in this contribution two other methods than the CCL, namely, the Precise Point Positioning (PPP) and the Array‐aided PPP (A‐PPP). The PPP further exploits the International GPS Service (IGS) orbit and clock products and turns out to be a geometry‐based method. The A‐PPP is designed to retrieve TECM from an array of colocated receivers, taking advantage of the broadcast orbit and clock products. Moreover, A‐PPP also takes into account the fact that the ionospheric effects measured from one satellite to all colocated receivers ought to be the same, thus leading to the estimability of interreceiver DCB. We perform a comparative study of the formal precision and the empirical accuracy of the TECM that are retrieved, respectively, by three methods from the same set of GPS data. Results of such a study can be used to assess the actual performance of the three methods. In addition, we check the temporal stability in A‐PPP‐derived interreceiver DCB estimates over time periods ranging from 1 to 3 days.

Improving capabilities of broadband differential satellite navigation systems via radio occultation technology

The existent satellite system for radio occultation monitoring the Earth’s neutral atmosphere and ionosphere (COSMIC) provides data to consumers in the regions with limited possibilities of constructing dense measurement networks (e.g., in the World Ocean area). A forthcoming increase of LEO small spacecrafts and the deployment of new satellite radio navigation systems will result in a pronounced increase in the efficiency of radio occultation method and its space resolution. As a result, the Space-Based Augmentation Systems (SBAS) broadband differential system will become global, or the quality of corrections delivered to single-frequency consumers of individual systems, e.g., the Augmentation and Monitoring System, will be improved. Therefore, the methods for processing and analyzing obtained radio occultation data should be improved. A simple method to reconstruct the electron density profile at radio occultation points, based on the total electron content measurement on the satellite–satellite path and the IRI-type ionospheric model has been proposed. The method needs initial information, it does not require refraction measurements, and it is free of the assumption that the ionosphere is spherically stratified in the occultation region. Verification of the proposed method based on data for 121 radio occultation cases across Europe in May 2013 demonstrated good agreement with the vertical sounding data.

Review and perspectives: Understanding natural‐hazards‐generated ionospheric perturbations using GPS measurements and coupled modeling

AbstractNatural hazards including earthquakes, volcanic eruptions, and tsunamis have been significant threats to humans throughout recorded history. Global navigation satellite systems (GNSS; including the Global Positioning System (GPS)) receivers have become primary sensors to measure signatures associated with natural hazards. These signatures typically include GPS‐derived seismic deformation measurements, coseismic vertical displacements, and real‐time GPS‐derived ocean buoy positioning estimates. Another way to use GPS observables is to compute the ionospheric total electron content (TEC) to measure, model, and monitor postseismic ionospheric disturbances caused by, e.g., earthquakes, volcanic eruptions, and tsunamis. In this paper, we review research progress at the Jet Propulsion Laboratory and elsewhere using examples of ground‐based and spaceborne observation of natural hazards that generated TEC perturbations. We present results for state‐of‐the‐art imaging using ground‐based and spaceborne ionospheric measurements and coupled atmosphere‐ionosphere modeling of ionospheric TEC perturbations. We also report advancements and chart future directions in modeling and inversion techniques to estimate tsunami wave heights and ground surface displacements using TEC measurements and error estimates. Our initial retrievals strongly suggest that both ground‐based and spaceborne GPS remote sensing techniques could play a critical role in detection and imaging of the upper atmosphere signatures of natural hazards including earthquakes and tsunamis. We found that combining ground‐based and spaceborne measurements may be crucial in estimating critical geophysical parameters such as tsunami wave heights and ground surface displacements using TEC observations. The GNSS‐based remote sensing of natural‐hazard‐induced ionospheric disturbances could be applied to and used in operational tsunami and earthquake early warning systems.

Near real‐time input to a propagation model for nowcasting of HF communications with aircraft on polar routes

AbstractThere is a need for improved techniques for nowcasting and forecasting (over several hours) HF propagation at northerly latitudes to support airlines operating over the increasingly popular trans‐polar routes. In this paper the assimilation of real‐time measurements into a propagation model developed by the authors is described, including ionosonde measurements and total electron content (TEC) measurements to define the main parameters of the ionosphere. The effects of D region absorption in the polar cap and auroral regions are integrated with the model through satellite measurements of the flux of energetic solar protons (>1 MeV) and the X‐ray flux in the 0.1–0.8 nm band, and ground‐based magnetometer measurements which form the Kp and Dst indices of geomagnetic activity. The model incorporates various features (e.g., convecting patches of enhanced plasma density) of the polar ionosphere that are, in particular, responsible for off‐great circle propagation and lead to propagation at times and frequencies not expected from on‐great circle propagation alone. The model development is supported by the collection of HF propagation measurements over several paths within the polar cap, crossing the auroral oval, and along the midlatitude trough.

The origin of infrasonic ionosphere oscillations over tropospheric thunderstorms

AbstractThunderstorms have been observed to introduce infrasonic oscillations in the ionosphere, but it is not clear what processes or which parts of the thunderstorm generate the oscillations. In this paper, we present a new technique that uses an array of ground‐based GPS total electron content (TEC) measurements to locate the source of the infrasonic oscillations and compare the source locations with thunderstorm features to understand the possible source mechanisms. The location technique utilizes instantaneous phase differences between pairs of GPS‐TEC measurements and an algorithm to best fit the measured and the expected phase differences for assumed source positions and other related parameters. In this preliminary study, the infrasound waves are assumed to propagate along simple geometric raypaths from the source to the measurement locations to avoid extensive computations. The located sources are compared in time and space with thunderstorm development and lightning activity. Sources are often found near the main storm cells, but they are more likely related to the downdraft process than to the updraft process. The sources are also commonly found in the convectively quiet stratiform regions behind active cells and are in good coincidence with extensive lightning discharges and inferred high‐altitude sprites discharges.

Analysis of the IMAGE RPI electron density data and CHAMP plasmasphere electron density reconstructions with focus on plasmasphere modelling

The electron density of the topside ionosphere and the plasmasphere contributes essentially to the overall Total Electron Content (TEC) budget affecting Global Navigation Satellite Systems (GNSS) signals. The plasmasphere can cause half or even more of the GNSS range error budget due to ionospheric propagation errors. This paper presents a comparative study of different plasmasphere and topside ionosphere data aiming at establishing an appropriate database for plasmasphere modelling. We analyze electron density profiles along the geomagnetic field lines derived from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite/Radio Plasma Imager (RPI) records of remote plasma sounding with radio waves. We compare these RPI profiles with 2D reconstructions of the topside ionosphere and plasmasphere electron density derived from GNSS based TEC measurements onboard the Challenging Minisatellite Payload (CHAMP) satellite. Most of the coincidences between IMAGE profiles and CHAMP reconstructions are detected in the region with L-shell between 2 and 5. In general the CHAMP reconstructed electron densities are below the IMAGE profile densities, with median of the CHAMP minus IMAGE residuals around −588cm−3. Additionally, a comparison is made with electron densities derived from passive radio wave RPI measurements onboard the IMAGE satellite. Over the available 2001–2005 period of IMAGE measurements, the considered combined data from the active and passive RPI operations cover the region within a latitude range of ±60°N, all longitudes, and an L-shell ranging from 1.2 to 15. In the coincidence regions (mainly 2⩽L⩽4), we check the agreement between available active and passive RPI data. The comparison shows that the measurements are well correlated, with a median residual of ∼52cm−3. The RMS and STD values of the relative residuals are around 22% and 21% respectively. In summary, the results encourage the application of IMAGE RPI data for plasmasphere and plasmapause modeling.

Analysis of traveling ionospheric disturbances (TIDs) in GPS TEC launched by the 2011 Tohoku earthquake

AbstractTraveling ionospheric disturbances (TIDs) have been detected using various measurement techniques, including HF sounders, incoherent scatter radars, in situ measurements, and optical techniques. However, observations of TIDs have tended to be sparse and there is a need for additional observations to provide new scientific insight into the geophysical source phenomenology and wave propagation physics. The dense network of GPS receivers around the globe offers a relatively new data source to observe and monitor TIDs. In this paper, we use total electron content (TEC) measurements from ~4000 GPS receivers throughout the continental United States to observe TIDs associated with the 11 March 2011 Tohoku tsunami. The tsunami propagated across the Pacific to the U.S. west coast over several hours, and we show that corresponding TIDs were observed in the US. Using this network of GPS receivers we present a 2D imaging of TEC perturbations and calculate various TID parameters, including horizontal wavelength, speed, and period. Well‐formed, planar TIDs were detected over the west coast of the U.S. ~10 h after the earthquake. Fast Fourier transform analysis of the observed waveforms revealed that the period of the wave was 15.1 min with a horizontal wavelength of 194.8 km, phase velocity of 233.0 m/s, and an azimuth of 105.2° (propagating nearly due east in the direction of the tsunami wave). These results are consistent with the TID observations in airglow measurements from Hawaii earlier in the day and with other GPS TEC observations.

Characteristics of GPS TEC variations in the polar cap ionosphere

AbstractThis paper presents statistical characteristics (occurrence rate, amplitude, and frequency) of low‐frequency (<100 mHz) variations in total electron content (TEC) observed in the polar cap ionosphere. TEC variations were primarily associated with mesoscale (tens to hundreds of kilometers) ionization structures and were observed by five Global Positioning System (GPS) receivers over a 6 year period (2009–2014). The altitude of ionization structures was estimated by using colocated ionosonde radars. High data rate receivers combined with broad spatial coverage of multisatellite TEC measurements provided high‐resolution magnetic local time/latitude maps of TEC variation characteristics, which were examined as a function of solar cycle and season. These high‐resolution maps improve upon the current observational picture of mesoscale structuring in the polar cap and provide accurate links to particular magnetospheric source regions. Occurrence of TEC variations was consistently highest in dayside regions mapping to low latitude and plasma mantle boundary layers, while largest‐amplitude TEC variations were observed in dayside regions close to the polar cusp, and lower latitudes around midnight. Occurrence and amplitude of TEC variations increased significantly during the ascending phase of the solar cycle, independent of solar wind conditions, while seasonal statistics showed highest dayside occurrence and amplitude in winter months, lowest in summer, and highest nightside occurrence and amplitude around equinox. A surprising result in the frequency distributions of TEC variations was discrete frequencies of about 2 and 4 mHz, which appeared to originate from regions corresponding to the plasma mantle, immediately poleward of the polar cusp.

Validation of NeQuick 2 model over the Kenyan region through data ingestion and the model application in ionospheric studies

NeQuick 2 is an ionospheric electron density model which provides electron density for a given location. Its output depends on solar activity expressed by 12-month running average sunspot number (R12) or solar radio flux (F10.7). To improve the model capabilities to reproduce electron density, data ingestion techniques have been implemented which replace the standard solar activity indices input with effective parameters that allow adapting a model to a certain data sets. In regions like the Sub-Saharan Africa where few observational data were available until recently, the performance of the ingested model needs some validation. This study investigates the performance of NeQuick 2 in the Kenya region, a low latitude region by assisting the model with total electron content measurement from a single GNSS station. These measurements are used to calculate effective ionization level parameters, which enable the difference between the measured and modeled TEC over the station to be less or equal to 0.5 TECU. The results show that by using computed effective parameters values as inputs in nearby stations, the model performance is greatly improved for both the low and moderate solar activity. This work has also demonstrated the capability of the model to describe spatial distribution of the total electron content in the low- latitude ionosphere.

Study of high-latitude ionosphere: One-year campaign over Husafell, Iceland

This paper reports on the effects of diurnal, seasonal, geomagnetic and solar activity on GPS Vertical Total Electron Content (VTEC) measurements at a high-latitude station in Husafell, Iceland (64.7°N, 21.0°W) from March 2009 to February 2010. According to the diurnal VTEC pattern, there was generally a build-up region at sunrise (0500-1000 LT), a daytime plateau in the afternoon (1200-1400 LT), and a decay region from evening to pre-dawn (1800-0400 LT). The month-to-month analysis showed high VTEC variability, particularly in February 2010, due to an increase in solar activity. The VTEC showed a high variability during both winter and the equinoxes, with the highest value being 90%, but showed a low variability in summer. Two abnormal peaks appeared at sunrise and sunset in winter and the equinoxes. These peaks were the result of steep density gradients caused by the onset and turnoff of solar radiation. The correlation analysis yielded almost no correlation between the VTEC and geomagnetic activity but showed a high correlation with solar activity for all the seasons, particularly at night-time.

A new source of the midlatitude ionospheric peak density structure revealed by a new Ionosphere‐Plasmasphere model

AbstractThe newly developed Ionosphere‐Plasmasphere (IP) model has revealed neutral winds as a primary source of the “third‐peak” density structure in the daytime global ionosphere that has been observed by the low‐latitude ionospheric sensor network GPS total electron content measurements over South America. This third peak is located near −30° magnetic latitude and is clearly separate from the conventional twin equatorial ionization anomaly peaks. The IP model reproduces the global electron density structure as observed by the FORMOSAT‐3/COSMIC mission. The model reveals that the third peak is mainly created by the prevailing neutral meridional wind, which flows from the summer hemisphere to the winter hemisphere lifting the plasma along magnetic field lines to higher altitudes where recombination is slower. The same prevailing wind that increases the midlatitude density decreases the low‐latitude density in the summer hemisphere by counteracting the equatorial fountain flow. The longitudinal variation of the three‐peak structure is explained by the displacement between the geographic and geomagnetic equators.

Mapping the East African Ionosphere Using Ground-based GPS TEC Measurements

The East African ionosphere (3°S-18°N, 32°E-50°E) was mapped using Total Electron Content (TEC) measurements from ground-based GPS receivers situated at Asmara, Mekelle, Bahir Dar, Robe, Arbaminch, and Nairobi. Assuming a thin shell ionosphere at 350 km altitude, we project the Ionospheric Pierce Point (IPP) of a slant TEC measurement with an elevation angle of >10° to its corresponding location on the map. We then infer the estimated values at any point of interest from the vertical TEC values at the projected locations by means of interpolation. The total number of projected IPPs is in the range of 24-66 at any one time. Since the distribution of the projected IPPs is irregularly spaced, we have used an inverse distance weighted interpolation method to obtain a spatial grid resolution of 1°×1° latitude and longitude, respectively. The TEC maps were generated for the year 2008, with a 2 hr temporal resolution. We note that TEC varies diurnally, with a peak in the late afternoon (at 1700 LT), due to the equatorial ionospheric anomaly. We have observed higher TEC values at low latitudes in both hemispheres compared to the magnetic equatorial region, capturing the ionospheric distribution of the equatorial anomaly. We have also confirmed the equatorial seasonal variation in the ionosphere, characterized by minimum TEC values during the solstices and maximum values during the equinoxes. We evaluate the reliability of the map, demonstrating a mean error (difference between the measured and interpolated values) range of 0.04-0.2 TECU (Total Electron Content Unit). As more measured TEC values become available in this region, the TEC map will be more reliable, thereby allowing us to study in detail the equatorial ionosphere of the African sector, where ionospheric measurements are currently very few.

Imaging the topside ionosphere and plasmasphere with ionospheric tomography using COSMIC GPS TEC

AbstractGPS‐based ionospheric tomography is a well‐known technique for imaging the total electron content (TEC) between GPS satellites and receivers. However, as an integral measurement of electron concentration, TEC typically encompasses both the ionosphere and plasmasphere, masking signatures from the topside ionosphere‐plasmasphere due to the dominant ionosphere. Imaging these regions requires a technique that isolates TEC in the topside ionosphere‐plasmasphere. Multi‐Instrument Data Analysis System (MIDAS) employs tomography to image the electron distribution in the ionosphere. Its implementation for regions beyond is yet to be seen due to the different dynamics present above the ionosphere. This paper discusses the extension of MIDAS to image these altitudes using GPS phase‐based TEC measurements and follows the work by Spencer and Mitchell (2011). Plasma is constrained to dipole field lines described by Euler potentials, resulting in a distribution symmetrical about the geomagnetic equator. A simulation of an empirical plasmaspheric model by Gallagher et al. (1988) is used to verify the technique by comparing reconstructions of the simulation with the empirical model. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) is used as GPS receiver locations. The verification is followed by a validation of the modified MIDAS algorithm, where the regions' TEC is reconstructed from COSMIC GPS phase measurements and qualitatively compared with previous studies using Jason‐1 and COSMIC data. Results show that MIDAS can successfully image features/trends of the topside ionosphere‐plasmasphere observed in other studies, with deviations in absolute TEC attributed to differences in data set properties and the resolution of the images.

Ionospheric response over Europe during the solar eclipse of March 20, 2015

The solar eclipse on March 20, 2015 was a fascinating event for people in Northern Europe. From a scientific point of view, the solar eclipse can be considered as an in situ experiment on the Earth’s upper atmosphere with a well-defined switching off and on of solar irradiation. Due to the strong changes in solar radiation during the eclipse, dynamic processes were initiated in the atmosphere and ionosphere causing a measurable impact, for example, on temperature and ionization. We analyzed the behavior of total ionospheric ionization over Europe by reconstructing total electron content (TEC) maps and differential TEC maps. Investigating the large depletion zone around the shadow spot, we found a TEC reduction of up to 6 TEC units, i.e., the total plasma depletion reached up to about 50%. However, the March 20, 2015 eclipse occurred during the recovery phase of a strong geomagnetic storm and the ionosphere was still perturbed and depleted. Therefore, the unusual high depletion is due to the negative bias of up to 20% already observed over Northern Europe before the eclipse occurred. After removing the negative storm effect, the eclipse-induced depletion amounts to about 30%, which is in agreement with previous observations. During the solar eclipse, ionospheric plasma redistribution processes significantly affected the shape of the electron density profile, which is seen in the equivalent slab thickness derived by combining vertical incidence sounding (VS) and TEC measurements. We found enhanced slab thickness values revealing, on the one hand, an increased width of the ionosphere around the maximum phase and, on the other, evidence for delayed depletion of the topside ionosphere. Additionally, we investigated very low frequency (VLF) signal strength measurements and found immediate amplitude changes due to ionization loss at the lower ionosphere during the eclipse time. We found that the magnitude of TEC depletion is linearly dependent on the Sun’s obscuration function. By modelling TEC depletion and knowing the Sun’s obscuration function in advance, Global Navigation Satellite System (GNSS) operators may improve the broadcast ionospheric correction during a solar eclipse day.

An empirical model of ionospheric total electron content (TEC) near the crest of the equatorial ionization anomaly (EIA)

We present a geomagnetic quiet time (Dst > −50 nT) empirical model of ionospheric total electron content (TEC) for the northern equatorial ionization anomaly (EIA) crest over Calcutta, India. The model is based on the 1980–1990 TEC measurements from the geostationary Engineering Test Satellite-2 (ETS-2) at the Haringhata (University of Calcutta, India: 22.58° N, 88.38° E geographic; 12.09° N, 160.46° E geomagnetic) ionospheric field station using the technique of Faraday rotation of plane polarized VHF (136.11 MHz) signals. The ground station is situated virtually underneath the northern EIA crest. The monthly mean TEC increases linearly with F10.7 solar ionizing flux, with a significantly high correlation coefficient (r = 0.89–0.99) between the two. For the same solar flux level, the TEC values are found to be significantly different between the descending and ascending phases of the solar cycle. This ionospheric hysteresis effect depends on the local time as well as on the solar flux level. On an annual scale, TEC exhibits semiannual variations with maximum TEC values occurring during the two equinoxes and minimum at summer solstice. The semiannual variation is strongest during local noon with a summer-to-equinox variability of ~50–100 TEC units. The diurnal pattern of TEC is characterized by a pre-sunrise (0400–0500 LT) minimum and near-noon (1300–1400 LT) maximum. Equatorial electrodynamics is dominated by the equatorial electrojet which in turn controls the daytime TEC variation and its maximum. We combine these long-term analyses to develop an empirical model of monthly mean TEC. The model is validated using both ETS-2 measurements and recent GNSS measurements. It is found that the present model efficiently estimates the TEC values within a 1-σ range from the observed mean values.

Statistics of Ionospheric Storms Using GPS TEC Measurements Between 2002 and 2014 in Jeju, Korea

Using the Total Electron Content (TEC) data from the Global Navigation Service System (GNSS) site in Jeju, operated by the Korea Astronomy and Space Science Institute (geographic location: , ; geomagnetic location: ) for 2002-2014 in Korea, the results of the statistical analysis of positive and negative ionospheric storms are presented for the first time. In this paper, ionospheric storms are defined as turbulences that exceed 50% of the percentage differential Global Positioning System (GPS) TEC ratio () with monthly median GPS TEC. During the period of observations, the total number of positive ionospheric storms ( > 50%) was 170, which is greater than five times the number of negative ionospheric storms (

Comparative study of GPS-TEC smoothing techniques

The availability of permanent global positioning system (GPS) stations makes the ionosphere monitoring and space weather studies more attainable. In order to obtain precise ionosphere total electron content (TEC) measurements, a smoothing technique has to be used. The objective of this research is to examine the accuracy and performance of two different TEC smoothing techniques; the carrier phase smoothed code and code levelled carrier phase techniques. GPS data from three stations in North America, located in different latitudes, are used. The accuracy of the smoothed TEC is compared with international GNSS service global ionospheric maps (IGS-GIM) and national oceanic and atmospheric administration (NOAA) ionospheric maps. The results reveal that the accuracy of the estimated TEC from the phase-smoothed code method depends upon the quality of data, number of observations used in the smoothing interval, receiver and satellite differential code biases (DCB). The levelled carrier phase method produces more calibrated TEC, however, with the influence of the systematic errors and the differential code biases.

ТЕПЛОВЫЕ И ДИНАМИЧЕСКИЕ ПРОЦЕССЫ В ИОНОСФЕРЕ ВО ВРЕМЯ ЧАСТНОГО ЗАТМЕНИЯ СОЛНЦА 20 МАРТА 2015 г. НАД ХАРЬКОВОМ. РЕЗУЛЬТАТЫ РАСЧЕТОВ

ТЕПЛОВЫЕ И ДИНАМИЧЕСКИЕ ПРОЦЕССЫ В ИОНОСФЕРЕ ВО ВРЕМЯ ЧАСТНОГО ЗАТМЕНИЯ СОЛНЦА 20 МАРТА 2015 г. НАД ХАРЬКОВОМ. РЕЗУЛЬТАТЫ РАСЧЕТОВ

Data assimilation of plasmasphere and upper ionosphere using COSMIC/GPS slant TEC measurements

AbstractIncreasing total electron content (TEC) measurements from the low Earth orbiting satellites to Global Positioning System satellites flourish the exploration of the ionosphere and plasmasphere for decades. This paper indicates a method that 3‐D Var is applied to assimilate precise orbit determination antenna TEC measurements of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites into the background global core plasma model (GCPM). The slant TEC data archived in the COSMIC Data Analysis and Archive Center from 500 km to 20,200 km are used to reconstruct a new electron density model. This model has a temporal resolution of 2 h and spatial resolutions of 2.5° in geomagnetic latitude, 5° in longitude, 50 km in the upper ionosphere, and several hundred kilometers in the plasmasphere. Preliminary results show that the data assimilation modifies the initial GCPM forecast to be better coincident with actual COSMIC measurements in internal quality check. Furthermore, independent validation with upper ionosphere‐retrieved electron density and TEC of global ionosphere maps implies a reasonable improvement in the estimation of plasmaspheric electron density after the assimilation.

A neural network based error correction method for radio occultation electron density retrieval

Abel inversion techniques have been widely employed to retrieve electron density profiles (EDPs) from radio occultation (RO) measurements, which are available by observing Global Navigation Satellite System (GNSS) satellites from low-earth-orbit (LEO) satellites. It is well known that the ordinary Abel inversion might introduce errors in the retrieval of EDPs when the spherical symmetry assumption is violated. The error, however, is case-dependent; therefore it is desirable to associate an error index or correction coefficient with respect to each retrieved EDP. Several error indices have been proposed but they only deal with electron density at the F2 peak and suffer from some drawbacks. In this paper we propose an artificial neural network (ANN) based error correction method for EDPs obtained by the ordinary Abel inversion. The ANN is first trained to learn the relationship between vertical total electron content (TEC) measurements and retrieval errors at the F2 peak, 220km and 110km altitudes; correction coefficients are then estimated to correct the retrieved EDPs at these three altitudes. Experiments using the NeQuick2 model and real FORMOSAT-3/COSMIC RO geometry show that the proposed method outperforms existing ones. Real incoherent scatter radar (ISR) measurements at the Jicamarca Radio Observatory and the global TEC map provided by the International GNSS Service (IGS) are also used to valid the proposed method.