Performance of the improved Abel transform to estimate electron density profiles from GPS occultation data

García-Fernández, Miquel; Hernández‐Pajares, M.; Zornoza, José Miguel Juan; Sanz, J.

doi:10.1007/s10291-005-0139-5

Cited by 22 publications

(16 citation statements)

References 12 publications

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“…Conventionally, the radio occultation (RO) technique is commonly used to obtain the electron density (Ne) in the ionosphere using the Abel integral equations [ Hajj and Romans , ; Schreiner et al ., , ; Tsai et al ., ; Syndergaard , ; Tsai and Tsai , ; Lei et al ., ]. Numerous studies about the assessment of ionospheric RO profiling have been reported by comparing with ground‐based ionosonde and incoherent scatter radar observations [ Hajj and Romans , ; Schreiner et al ., ; Tsai et al ., ; Jakowski et al ., ; Garcia‐Fernandez et al ., , ; Lei et al ., ; Kelley et al ., ]. A review of the literature indicated that the peak density and height of the F region (NmF2 and hmF2) obtained from GPS RO observation have a root‐mean‐square error of 10–20%.…”

Section: Introductionmentioning

confidence: 99%

“…[] and Garcia‐Fernandez et al . [, ] have used the shape scaling function to convert vertical total electron content (VTEC) from the global ionosphere map (GIM) to electron density and introduced them as the horizontal information for the Abel inversion. They indicated the improvement of about 30% on the maximum of plasma frequency (foF2) with the aided horizontal information to Abel inversion.…”

Section: Introductionmentioning

confidence: 99%

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Ionospheric electron density inversion for Global Navigation Satellite Systems radio occultation using aided Abel inversions

et al. 2017

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The Abel inversion of ionospheric electron density profiles with the assumption of spherical symmetry applied for radio occultation soundings could introduce a greater systematic error or sometimes artifacts if the occultation rays trespass regions with larger horizontal gradients in electron density. The aided Abel inversions have been proposed by considering the asymmetry ratio derived from ionospheric total electron content (TEC) or peak density (NmF2) of reconstructed observation maps since knowledge of the horizontal asymmetry in ambient ionospheric density could mitigate the inversion error. Here we propose a new aided Abel inversion using three‐dimensional time‐dependent electron density (Ne) based on the climatological maps constructed from previous observations, as it has an advantage of providing altitudinal information on the horizontal asymmetry. Improvement of proposed Ne‐aided Abel inversion and comparisons with electron density profiles inverted from the NmF2‐ and TEC‐aided inversions are studied using observation system simulation experiments. Comparison results show that all three aided Abel inversions improve the ionospheric profiling by mitigating the artificial plasma caves and negative electron density in the daytime E region. The equatorial ionization anomaly crests in the F region become more distinct. The statistical results show that the Ne‐aided Abel inversion has less mean and RMS error of error percentage above 250 km altitudes, and the performances for all aided Abel inversions are similar below 250 km altitudes.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ionospheric electron density inversion for Global Navigation Satellite Systems radio occultation using aided Abel inversions

et al. 2017

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“…This quality has been assessed globally and by considering two specific regions where the performance of the GIMs is expected to be different from global performance. Previously published studies (Aragon‐Angel et al, ; García‐Fernández et al, , ; Yue et al, ) suggested that the improvement of the SM, with regard to the classic approach, is small and/or essentially due to the LoC error, which is substantially mitigated when the SM is used. However, our results do not agree with this interpretation.…”

Section: Discussionmentioning

confidence: 99%

“…Thanks to this strategy, the SM is able to calculate vertical EDPs, unlike previously mentioned methods that only calculate oblique EDPs. Using the SM, García‐Fernández et al (, ) and Aragon‐Angel et al () compared the results of RO retrieved N e with ionosonde measurements of N m F 2 and reported average improvements of 30 and 45%, respectively, over the results obtained from the classic approach. However, in a subsequent study, using data from the Jicamarca ionosonde near the magnetic equator, Aragon‐Angel et al () found a 10% improvement when using a narrow window to collocate the RO retrieved EDPs that were used in the comparison.…”

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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“…It shows a great improvement when this method is applied to the retrievals of simulated data, but it is difficult to obtain a precise 3‐D constraint to achieve a good improvement when it is applied to the retrievals of real observation data [ Schreiner et al , 1999; Wu et al , 2008]. Hernandez‐Pajares et al [2000] proposed a modified Abel algorithm with the constraint of the vertical TEC data from ground GPS observation, which made some improvements [ Garcia‐Fernandez et al , 2003, 2005]. Tsai and Tsai [2004] proposed a method using the electron density profiles from nearby occultation events to compensate for the horizontal asymmetry.…”

Section: Introductionmentioning

confidence: 99%

An asymmetry correction method for ionospheric radio occultation

Gong

et al. 2009

J. Geophys. Res.

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[1] The approximation of spherical symmetry of electron density is the main error source in the inversion of ionospheric radio occultation (IRO). The study in this paper shows that only even terms of the asymmetry contribute to the inversion error. An asymmetry factor for IRO is defined, and it is approximately equal to the relative error of the inversion result. The characteristics of the asymmetry factor are studied and are shown in the following: (1) the absolute value of asymmetry factor (AVAF) of a zonal occultation is much smaller than that of the meridian one; (2) higher solar activity corresponds to larger AVAF; (3) AVAF is largest in winter, second largest in equinox season, and smallest in summer; and (4) generally, AVAF at middle geomagnetic latitudes is smaller than at other latitudes, and it is large at the magnetic equator, the crest region, and the middle-latitude trough. The asymmetry factor is applied to correct the retrieved electron density, and the inversion error is greatly reduced.

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Performance of the improved Abel transform to estimate electron density profiles from GPS occultation data

Cited by 22 publications

References 12 publications

Ionospheric electron density inversion for Global Navigation Satellite Systems radio occultation using aided Abel inversions

Ionospheric electron density inversion for Global Navigation Satellite Systems radio occultation using aided Abel inversions

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

An asymmetry correction method for ionospheric radio occultation

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