Validation and Improvement of NeQuick Topside Ionospheric Formulation Using COSMIC/FORMOSAT‐3 Data

Singh, Arun Kumar; Haralambous, Haris; Oikonomou, Christina

doi:10.1029/2020ja028720

Cited by 8 publications

(10 citation statements)

References 51 publications

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“…Singh et al. (2021) studied the effect of g parameter on the topside profiles and proposed that a constant g value of 0.15 instead of 0.125 gives better estimates. In the present study, comparison of the influence of three empirical parameters on the topside profiles indicated that, modifications in Ho significantly affects the topside electron density distribution when the g and r , are kept constant, especially over the equatorial and low latitudes.…”

Section: Discussionmentioning

confidence: 99%

“…The third empirical parameter, r, is mainly defined to control the scale height increase at greater heights and hence does not show any significant influence on the topside profiles in the height range up to 1,000 km, considered in the present analysis. Singh et al (2021) studied the effect of g parameter on the topside profiles and proposed that a constant g value of 0.15 instead of 0.125 gives better estimates. In the present study, comparison of the influence of three empirical parameters on the topside profiles indicated that, modifications in Ho significantly affects the topside electron density distribution when the g and r, are kept constant, especially over the equatorial and low latitudes.…”

Section: Discussionmentioning

confidence: 99%

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Parametric Dependence of Topside Ionospheric Empirical Scale Height and Electron Density Profiles in NeQuick2 Model Over the Equatorial and Low Latitudes and Its Consequences on the Estimation of TEC

Venkatesh,

Pallamraju,

Pant

et al. 2023

JGR Space Physics

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Constructing realistic vertical electron density profiles is a crucial step in accurately estimating the ionospheric Total Electron Content (TEC) in empirical models. Inadequate representation of electron density profiles leads to under‐ or over‐estimation of TEC in model outputs. One of the widely used ionospheric empirical model, the NeQuick2 exhibits large uncertainties over equatorial and low latitudes, particularly in the topside ionosphere. The NeQuick2 model employs semi Epstein type of polynomials to characterize the topside ionospheric structure, wherein, the scale height (H) is the key parameter. NeQuick2 model estimates H value using empirical formulations, which contain three major parameters namely, Ho – the scale height at the F‐layer peak, g – height gradient in H, and r – which controls the increase in H at higher altitudes. In this study, a systematic analysis has been carried out with particular focus on the equatorial and low latitudes to explore the variability of topside scale height and electron density profiles on the above three empirical parameters using COSMIC observations over Trivandrum and Ahmedabad, in India. Model uncertainties in estimating Ho and their impacts on the estimation of TEC are investigated. Data assimilation analysis has been carried out to obtain a quantitative understanding on the effect of deviations in topside scale height on the uncertainties in accurate estimation of TEC over equatorial and low latitudes. This study reveals the impact of scale height uncertainties on errors in modelled TEC and demonstrates the need for improvement in empirical formulations for improving accuracies in ionospheric modelling over equatorial and low latitude sectors.This article is protected by copyright. All rights reserved.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Parametric Dependence of Topside Ionospheric Empirical Scale Height and Electron Density Profiles in NeQuick2 Model Over the Equatorial and Low Latitudes and Its Consequences on the Estimation of TEC

Venkatesh,

Pallamraju,

Pant

et al. 2023

JGR Space Physics

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“…This overestimation was particularly noticeable during summer (June) [22]. Another recent study on the topside ionosphere over Cyprus indicated that NeQuick provides a superior representation than the a-Chapman function embedded in the Cyprus Digisonde Automatic Real-Time Ionogram Scaler with True height (ARTIST) software [9,23].…”

Section: Methodsmentioning

confidence: 99%

“…The NeQuick model was adopted as the basis of the real-time ionospheric correction model algorithm (NeQuick-G) used for Galileo single-frequency positioning ionospheric correction [6]. Despite certain developments, that have been applied in the NeQuick formulation during its evolution [7], several recent studies have demonstrated that there is still room for further improvement [8,9].…”

Section: Introductionmentioning

confidence: 99%

Adjusting CCIR Maps to Improve Local Behaviour of Ionospheric Models

et al. 2021

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The objective of this article is to present a concept for single-frequency Global Navigation Satellite System (GNSS) positioning local ionospheric mitigation over a certain area. This concept is based on input parameters driving the NeQuick-G algorithm (the ionospheric single-frequency GNSS correction algorithm adopted by Galileo GNSS system), estimated on a local as opposed to a global scale, from ionospheric characteristics measured by a digital ionosonde and a collocated dual-frequency Total Electron Content (TEC) monitor. This approach facilitates the local adjustment of Committee Consultative for Ionospheric Radiowave propagation (CCIR) files and the Az ionization level, which control the ionospheric electron density profile in NeQuick-G, therefore enabling better estimation of positioning errors under quiet geomagnetic conditions. This novel concept for local ionospheric positioning error mitigation may be adopted at any location where ionospheric characteristics foF2 and M(3000)F2 can be measured, as a means to enhance the accuracy of single-frequency positioning applications based on the NeQuick-G algorithm.

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“…Since the original NeQuick models H 0 as a function of the bottomside thickness parameter [40,41], it exhibits a strong coupling between the bottomside and the topside part of the ionosphere, which in some cases causes inaccurate results [33,42,43]. The new formulation H 0,corr , also based on in-situ measurements, improved the performance of the NeQuick topside representation at middle latitudes [35,44] and low latitudes [45,46].…”

Section: Introductionmentioning

confidence: 99%

An Update of the NeQuick-Corr Topside Ionosphere Modeling Based on New Datasets

Pezzopane,

Pignalberi,

Pietrella

et al. 2024

Atmosphere

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A new analytical formula for H0, one of the three parameters (H0, g, and r) on which the NeQuick model is based to describe the altitude profile of the electron density above the F2-layer peak height hmF2, has recently been proposed. This new analytical representation of H0, called H0,corr, relies on numerical grids based on two different types of datasets. On one side, electron density observations by the Swarm satellites over Europe from December 2013 to September 2018, and on the other side, IRI UP (International Reference Ionosphere UPdate) maps over Europe of the critical frequency of the ordinary mode of propagation associated with the F2 layer, foF2, and hmF2, at 15 min cadence for the same period. The new NeQuick topside representation based on H0,corr, hereafter referred to as NeQuick-corr, improved the original NeQuick topside representation. This work updates the numerical grids of H0,corr by extending the underlying Swarm and IRI UP datasets until December 2021, thus allowing coverage of low solar activity levels, as well. Moreover, concerning Swarm, besides the original dataset, the calibrated one is considered, and corresponding grids of H0,corr calculated. At the same time, the role of g is investigated, by considering values different from the reference one, equal to 0.125, currently adopted. To understand what are the best H0,corr grids to be considered for the NeQuick-corr topside representation, vertical total electron content data for low, middle, and high latitudes, recorded from five low-Earth-orbit satellite missions (COSMIC/FORMOSAT-3, GRACE, METOP, TerraSAR-X, and Swarm) have been analyzed. The updated H0,corr grids based on the original Swarm dataset with a value for g = 0.15, and the updated H0,corr grids based on the calibrated Swarm dataset with a value for g = 0.14, are those for which the best results are obtained. The results show that the performance of the different NeQuick-corr models is reliable also for low latitudes, even though these are outside the spatial domain for which the H0,corr grids were obtained, and are dependent on solar activity.

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Validation and Improvement of NeQuick Topside Ionospheric Formulation Using COSMIC/FORMOSAT‐3 Data

Cited by 8 publications

References 51 publications

Parametric Dependence of Topside Ionospheric Empirical Scale Height and Electron Density Profiles in NeQuick2 Model Over the Equatorial and Low Latitudes and Its Consequences on the Estimation of TEC

Parametric Dependence of Topside Ionospheric Empirical Scale Height and Electron Density Profiles in NeQuick2 Model Over the Equatorial and Low Latitudes and Its Consequences on the Estimation of TEC

Adjusting CCIR Maps to Improve Local Behaviour of Ionospheric Models

An Update of the NeQuick-Corr Topside Ionosphere Modeling Based on New Datasets

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