Improvement of GPS/MET Ionospheric Profiling and Validation Using the Chung-Li Ionosonde Measurements and the IRI model

Tsai, Lung Chih; Tsai, Wei Hsiung

doi:10.3319/tao.2004.15.4.589(a)

Cited by 50 publications

(47 citation statements)

References 21 publications

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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%

“…The electron density profile (EDP) is one of the most important products for space weather and ionospheric science. In order to retrieve EDP from the integrated slant total electron content (TEC), many different methods have been applied (e.g., Hernández-Pajares et al, 2000;Schreiner et al, 1999;Tsai and Tsai, 2004;Wu et al, 2009b), but Abel inversion is the most commonly used technique.…”

Section: Introductionmentioning

confidence: 99%

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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%

Section: Introductionmentioning

confidence: 99%

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

et al. 2010

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“…The obtained observations contain information on the vertical refractivity below the LEO orbit and therefore enable the extraction of electron density profiles, which can be derived from the ionospheric index of refraction. Retrieval methods have been described in several publications such as Jakowski et al (2002) or Tsai and Tsai (2004). The derived profiles contain discrete N e observations that structurally describe the electron density distribution along the measured points.…”

Section: Introductionmentioning

confidence: 99%

Regional representation of F2 Chapman parameters based on electron density profiles

Limberger¹,

Wu²,

Schmidt³

et al. 2013

Ann. Geophys.

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Abstract. Understanding the physical processes within the ionosphere is a key requirement to improve and extend ionospheric modeling approaches. The determination of meaningful parameters to describe the vertical electron density distribution and how they are influenced by the solar activity is an important topic in ionospheric research. In this regard, the F2 layer of the ionosphere plays a key role as it contains the highest concentration of electrons and ions. In this contribution, the maximum electron density NmF2, peak height hmF2 and scale height HF2 of the F2 layer are determined by employing a model approach for regional applications realized by the combination of endpoint-interpolating polynomial B splines with an adapted physics-motivated Chapman layer. For this purpose, electron density profiles derived from ionospheric GPS radio occultation measurements of the satellite missions FORMOSAT-3/COSMIC, GRACE and CHAMP have been successfully exploited. Profiles contain electron density observations at discrete spots, in contrast to the commonly used integrated total electron content from GNSS, and therefore are highly sensitive to obtaining the required information of the vertical electron density structure. The spatio-temporal availability of profiles is indeed rather sparse, but the model approach meets all requirements to combine observation techniques implicating the mutual support of the measurements concerning accuracy, sensitivity and data resolution. For the model initialization and to bridge observation gaps, the International Reference Ionosphere 2007 is applied. Validations by means of simulations and selected real data scenarios show that this model approach has significant potential and the ability to yield reliable results.

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“…Research facilities, such as the Universitat Politécnica de Catalunya (UPC, Spain) or the Center for Space and Remote Sensing Research (CSRSR, Taiwan), perform an independent retrieval based on improved Abel inversion techniques under consideration of horizontal ionospheric gradients. The CSRSR approach is based on the interpolation of information from nearby EDPs with a cubic spline fit (Tsai & Tsai 2004) while the UPC method considers the Vertical Total Electron Content (VTEC) derived from terrestrial GNSS observations (Hernández-Pajares et al 2000). The latter approach is capable of improving the retrieval algorithm with relatively low implementation effort under support of global ionosphere maps (GIMs) as shown, for instance, by Hernán-dez-Pajares et al (2000), Garcia-Fernandez et al (2003), and Aragon-Angel (2010).…”

Section: Introductionmentioning

confidence: 99%

Long-term comparison of the ionospheric F2 layer electron density peak derived from ionosonde data and Formosat-3/COSMIC occultations

Limberger¹,

Hernández‐Pajares

Aragón‐Àngel

et al. 2015

J. Space Weather Space Clim.

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Electron density profiles (EDPs) derived from GNSS radio occultation (RO) measurements provide valuable information on the vertical electron density structure of the ionosphere and, among others, allow the extraction of key parameters such as the maximum electron density NmF2 and the corresponding peak height hmF2 of the F2 layer. An efficient electron density retrieval method, developed at the UPC (Barcelona, Spain), has been applied in this work to assess the accuracy of NmF2and hmF2 as determined from Formosat-3/COSMIC (F-3/C) radio occultation measurements for a period of more than half a solar cycle be- ) and local times (LT) accounting for different ionospheric conditions at night (02:00 LT ± 2 h), dawn (08:00 LT ± 2 h), and day (14:00 LT ± 2 h). The mean differences of F2 layer electron density peaks observed by F-3/C and ionosondes are found to be insignificant. Relative variations of the peak differences are determined in the range of 22%-30% for NmF2 and 10%-15% for hmF2. The consistency of observations is generally high for the equatorial and mid-latitude sectors at daytime and dawn whereas degradations have been detected in the polar regions and during night. It is shown, that the global averages of NmF2 and hmF2 derived from F-3/C occultations appear as excellent indicators for the solar activity.

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Improvement of GPS/MET Ionospheric Profiling and Validation Using the Chung-Li Ionosonde Measurements and the IRI model

Cited by 50 publications

References 21 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

Regional representation of F2 Chapman parameters based on electron density profiles

Long-term comparison of the ionospheric F2 layer electron density peak derived from ionosonde data and Formosat-3/COSMIC occultations

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