Estimating <i>E</i> region density profiles from radio occultation measurements assisted by IDA4D

Nicolls, M. J.; Rodrigues, F. S.; Bust, G. S.; Chau, Jorge L.

doi:10.1029/2009ja014399

Cited by 25 publications

(27 citation statements)

References 45 publications

(71 reference statements)

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“…Improvements are currently under investigation at the CDAAC. Some new and improved retrieval methods, such as adding other observations or nearby occultation observations or modeling results to provide horizontal gradient (Hernández-Pajares et al, 2000;Schreiner et al, 1999;Tsai and Tsai, 2004), correcting the retrieved EDPs by making use of the relationship between retrieval error and electron density asymmetry (Wu et al, 2009b), or data assimilation method (Nicolls et al, 2009), will be applied and compared in a future study.…”

Section: Resultsmentioning

confidence: 99%

Error analysis of Abel retrieved electron density profiles from radio occultation measurements

et al. 2010

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Abstract. This letter reports for the first time the simulated error distribution of radio occultation (RO) electron density profiles (EDPs) from the Abel inversion in a systematic way. Occultation events observed by the COSMIC satellites are simulated during the spring equinox of 2008 by calculating the integrated total electron content (TEC) along the COS-MIC occultation paths with the "true" electron density from an empirical model. The retrieval errors are computed by comparing the retrieved EDPs with the "true" EDPs. The results show that the retrieved NmF2 and hmF2 are generally in good agreement with the true values, but the reliability of the retrieved electron density degrades in low latitude regions and at low altitudes. Specifically, the Abel retrieval method overestimates electron density to the north and south of the crests of the equatorial ionization anomaly (EIA), and introduces artificial plasma caves underneath the EIA crests. At lower altitudes (E-and F1-regions), it results in three pseudo peaks in daytime electron densities along the magnetic latitude and a pseudo trough in nighttime equatorial electron densities.

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Section: Resultsmentioning

confidence: 99%

Error analysis of Abel retrieved electron density profiles from radio occultation measurements

et al. 2010

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“…The most straightforward methods make use of information on the structure of the ionosphere horizontal gradients in order to perform an aided Abel inversion. This approach has typically relied on either empirical models, such as the International Reference Ionosphere (IRI), vertical total electron content (VTEC) maps, or a combination of empirical models and observations [e.g., Hernandez‐Pajares et al , ; Garcia‐Fernandez et al , ; Nicolls et al , ; Yue et al , ; Guo et al , ; Wu et al , ]. Constraining the inversion through a priori information of the three‐dimensional structure of the ionosphere has also been employed [e.g., Hajj et al , ; Schreiner et al , ]; however, Schreiner et al [] found no statistical improvement of this approach compared to the standard Abel inversion when compared to ionosonde observations of the F region peak.…”

Section: Introductionmentioning

confidence: 99%

An improved inversion for FORMOSAT‐3/COSMIC ionosphere electron density profiles

2015

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An improved method to retrieve electron density profiles from Global Positioning System (GPS) radio occultation (RO) data is presented and applied to Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) observations. The improved inversion uses a monthly grid of COSMIC F region peak densities (NmF2), which are obtained via the standard Abel inversion, to aid the Abel inversion by providing information on the horizontal gradients in the ionosphere. This lessens the impact of ionospheric gradients on the retrieval of GPS RO electron density profiles, reducing the dominant error source in the standard Abel inversion. Results are presented that demonstrate the NmF2 aided retrieval significantly improves the quality of the COSMIC electron density profiles. Improvements are most notable at E region altitudes, where the improved inversion reduces the artificial plasma cave that is generated by the Abel inversion spherical symmetry assumption at low latitudes during the daytime. Occurrence of unphysical negative electron densities at E region altitudes is also reduced. Furthermore, the NmF2 aided inversion has a positive impact at F region altitudes, where it results in a more distinct equatorial ionization anomaly. COSMIC electron density profiles inverted using our new approach are currently available through the University Corporation for Atmospheric Research COSMIC Data Analysis and Archive Center. Owing to the significant improvement in the results, COSMIC data users are encouraged to use electron density profiles based on the improved inversion rather than those inverted by the standard Abel inversion.

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“…It can result in several large‐scale pseudofeatures such as two plasma caves underneath the equatorial ionization anomaly (EIA) crests, three peaks along the latitude in the low‐altitude regions, and the reversal phase wave number 4 structure in the E and F1 layers [ Lei et al , 2010; Yue et al , 2010, 2011b]. Many different revised methods, such as the data assimilation retrieval by Yue et al [2011a] and Nicolls et al [2009], the maximum entropy method by Hysell [2007], incorporating horizontal gradients by other types of observations by Schreiner et al [1999] and Hernandez‐Pajares et al [2000], joint retrieval of several occultations by Hocke and Igarashi [2002] and Tsai and Tsai [2004], have been proposed to improve the RO EDP retrieval.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the orbit altitude electron density estimation and its effect on the Abel inversion from radio occultation measurements

et al. 2011

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[1] In this paper, the observations from CHAMP radio occultation (RO) and Planar Langmuir Probe (PLP) during [2002][2003][2004][2005][2006][2007][2008] and Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) observations during 2007. 090-2007.120 are used to evaluate the orbit altitude electron density estimation and its effect on the Abel inversion from RO measurements. Comparison between PLP observed and RO estimated orbit electron density on board CHAMP shows that RO estimation tends to overestimate the true orbit electron density by 10% averagely. The average relative deviation is ∼20% and decreases slightly with the increase of the ionospheric peak height and the satellite orbit. It is larger at nighttime than daytime and peaks around sunrise time. Simulations based on COSMIC observations using NeQuick model indicate that the solar activity and the satellite orbit altitude variations will not influence the ratio of the successfully retrieved electron density profiles to the observed occultation events and the relative Abel inversion error of the electron density as well. Different orbit electron density derivation methods, including estimation by the RO total electron content, given by an independent on orbit observation, and assumed to be equal to the topmost point, will have no essential influence on the Abel retrieved electron density. Adding an on orbit observation even has a negative effect on the Abel retrieved electron density around the orbit altitude, which is contrary to our imagination.Citation: Yue, X., W. S. Schreiner, C. Rocken, and Y.-H. Kuo (2011), Evaluation of the orbit altitude electron density estimation and its effect on the Abel inversion from radio occultation measurements, Radio Sci., 46, RS1013,

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Estimating E region density profiles from radio occultation measurements assisted by IDA4D

Cited by 25 publications

References 45 publications

Error analysis of Abel retrieved electron density profiles from radio occultation measurements

Error analysis of Abel retrieved electron density profiles from radio occultation measurements

An improved inversion for FORMOSAT‐3/COSMIC ionosphere electron density profiles

Evaluation of the orbit altitude electron density estimation and its effect on the Abel inversion from radio occultation measurements

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