Two‐component model of topside ionosphere electron density profiles retrieved from Global Navigation Satellite Systems radio occultations

González-Casado, Guillermo; Zornoza, José Miguel Juan; Hernández‐Pajares, Manuel; Sanz, J.

doi:10.1002/2013ja019099

Cited by 9 publications

(39 citation statements)

References 23 publications

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“…More often than not, above the maximum, the data is more linearly correlated with height than below. Therefore, we focused the analysis on the heights above h m and below the transition height to the plasmasphere [see, e.g., González‐Casado et al , ], which is the ionospheric region where the single Chapman layer hypothesis is more realistic.…”

Section: Methodsmentioning

confidence: 99%

A linear scale height Chapman model supported by GNSS occultation measurements

et al. 2016

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Global Navigation Satellite Systems (GNSS) radio occultations allow the vertical sounding of the Earth's atmosphere, in particular, the ionosphere. The physical observables estimated with this technique permit to test theoretical models of the electron density such as, for example, the Chapman and the Vary‐Chap models. The former is characterized by a constant scale height, whereas the latter considers a more general function of the scale height with respect to height. We propose to investigate the feasibility of the Vary‐Chap model where the scale height varies linearly with respect to height. In order to test this hypothesis, the scale height data provided by radio occultations from a receiver on board a low Earth orbit (LEO) satellite, obtained by iterating with a local Chapman model at every point of the topside F2 layer provided by the GNSS satellite occultation, are fitted to height data by means of a linear least squares fit (LLS). Results, based on FORMOSAT‐3/COSMIC GPS occultation data inverted by means of the Improved Abel transform inversion technique (which takes into account the horizontal electron content gradients) show that the scale height presents a more clear linear trend above the F2 layer peak height, hm, which is in good agreement with the expected linear temperature dependence. Moreover, the parameters of the linear fit obtained during four representative days for all seasons, depend significantly on local time and latitude, strongly suggesting that this approach can significantly contribute to build realistic models of the electron density directly derived from GNSS occultation data.

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Section: Methodsmentioning

confidence: 99%

A linear scale height Chapman model supported by GNSS occultation measurements

et al. 2016

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“…The details of the methodology applied in this study can be found in [3] and [4], we only summarize here the details required to understand how the ionospheric and plasmaspheric electron contents are calculated and the data required to implement the method. First, the improved Abel transform inversion ( [3], [6]) is used to retrieve electron density profiles from a data sample of RO measurements taken by the CF3 constellation.…”

Section: Data Sample and Methodsmentioning

confidence: 99%

“…After the bottom-side plasmaspheric electron density was separated, the remaining electron density profile was integrated to obtain the ionospheric electron content, EC ion . Finally, after having calculated EC ion , the plasmaspheric electron content, EC pl , is calculated as the difference [4]:…”

Section: Data Sample and Methodsmentioning

confidence: 99%

“…Hence, the characterization of the separated electron content from the ionosphere and the plasmasphere is of great importance to achieve a precise modeling of the GNSS signal delays. Recently ( [3], [4]), a method that self-consistently combines radio occultations (ROs) from the COSMIC/FORMOSAT-3 (CF3) constellation and global ionospheric maps (GIMs) [5] from the International GNNS Service (IGS) has been developed to achieve a reliable determination of the electron contents in the ionospheric and plasmaspheric regions separately.…”

Section: Introductionmentioning

confidence: 99%

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Ionosphere/plasmasphere sounding with ground and space-based GNSS observations

González-Casado

Zornoza

Sanz

et al. 2016

2016 International Conference on Localization and GNSS (ICL-GNSS)

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Abstract-Applying a methodology developed and tested in previous studies, the contribution from the ionospheric and plasmaspheric regions to the total electron content (measured by ground receivers) is analyzed. The method is based in the electron density profiles retrieved from radio occultations observed with low Earth orbit satellites, combined with an accurate empirical modeling of the topside-ionosphere electron density. The results of a climatological study of the fractional electron content from the ionospheric region are presented for a year of low solar activity. It is shown that a simple parametric model can be used to reproduce the electron content variations in the ionosphere and the plasmasphere between sunrise and midday, the period of the day showing the largest electron content variability.

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“…On the other hand, according to González‐Casado et al (), the EDP retrievals from ROs depend only on the electron content (EC) below the LEO so that the EC above the LEO only affects the N e retrievals at the altitudes near the LEO height. However, this finding implies that the TEC‐aided inversion could be affected by some mismodeling because TEC is used instead of EC below the LEO satellite height to describe the horizontal gradient in the electron density around the tangent points of the RO.…”

Section: Introductionmentioning

confidence: 99%

Improvement of the Ionospheric Radio Occultation Retrievals by Means of Accurate Global Ionospheric Maps

et al. 2018

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The Abel inversion method is the classic approach to retrieve electron density profiles from radio occultation measurements, assuming that the electron density is only dependent upon height. In the early 2000s, the total electron content (TEC)‐aided inversion method was introduced, where horizontal gradients in the electron density distribution are taken into account by using information from an external model of total electron content (TEC). We show how the quality of the chosen external ionospheric model influences the radio occultation retrievals. Using a two‐layer TEC model, the 68% percentiles of the global error distributions of retrieved critical frequency and bottomside ionospheric electron content for 2014 improve more than 30%, with regard to the classic Abel inversion results. In a well‐sounded region like Europe, this improvement raises to about 40–45%, while 10% improvement is achieved using two‐layer maps with regard to the retrievals using single‐layer TEC maps. We point out that using the TEC to describe the horizontal gradient incurs an implicit mismodeling that, until now, has not been taken into account. A new technique is presented that, thanks to TEC modeling by means of two layers, can assess the impacts of such mismodeling. From this technique, a method to select the most accurate radio occultation retrievals is applied to demonstrate that the resulting errors in the retrieved critical frequencies for the European region are smaller than 7% in nearly 82% of the cases, very similar to the relative difference between measurements of two nearby ionosondes.

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Two‐component model of topside ionosphere electron density profiles retrieved from Global Navigation Satellite Systems radio occultations

Cited by 9 publications

References 23 publications

A linear scale height Chapman model supported by GNSS occultation measurements

A linear scale height Chapman model supported by GNSS occultation measurements

Ionosphere/plasmasphere sounding with ground and space-based GNSS observations

Improvement of the Ionospheric Radio Occultation Retrievals by Means of Accurate Global Ionospheric Maps

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