Ionospheric electron density profiles obtained with the Global Positioning System: Results from the GPS/MET experiment

Hajj, G. A.; Romans, L.J.

doi:10.1029/97rs03183

Cited by 366 publications

(339 citation statements)

References 14 publications

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“…Since the index of refractivity of the ionosphere depends mainly on the number of free electrons, the inversion of the measured signals can provide the vertical electron density profile (e.g. Hajj and Romans, 1998;Schreiner et al, 1999;Jakowski et al, 2002). Radio occultation measurements onboard CHAMP have been used since April 2002 to retrieve…”

Section: Introductionmentioning

confidence: 99%

Enhanced E-layer ionization in the auroral zones observed by radio occultation measurements onboard CHAMP and Formosat-3/COSMIC

Mayer

Jakowski

2009

Ann. Geophys.

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Abstract. Particle precipitation of magnetospheric origin causes additional ionization in the auroral zone at E-layer heights. During night-time, in particular at winter-night, the E-layer ionization may dominate over the F2-layer ionization level. To study the geophysical conditions and characteristics of the related ionospheric processes in more detail, we use GPS radio occultation electron density profile retrievals from CHAMP and Formosat-3/COSMIC to extract those vertical profiles which show the absolute maximum of ionization in the E-layer height range of 90-150 km. In order to select these profiles, we have developed an algorithm which can recognize the shape of a given profile by fitting an empirical Ansatz to it. Using data from CHAMP collected since 2002 and Formosat-3/COSMIC data starting from 2006, we are able to study both, the local-time dependence and the solarcylce variability of the observed processes.

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Section: Introductionmentioning

confidence: 99%

Enhanced E-layer ionization in the auroral zones observed by radio occultation measurements onboard CHAMP and Formosat-3/COSMIC

Mayer

Jakowski

2009

Ann. Geophys.

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“…The Abel inversion (cf. Hajj and Romans, 1998) has been employed to invert the electron density from the RO TEC. With the success of F3/C, the United States and Taiwan are moving forward with a follow-on RO mission named FORMOSAT-7/COSMIC-2 (F7/C2), which will ultimately place 12 satellites in orbit with two launches with 24-28.5 • inclination and 520-550 km altitude in 2016 and with 72 • inclination and 720-750 km altitude in 2018 (Lee et al, 2013;Yue et al, 2014;Yen, 2015).…”

Section: Introductionmentioning

confidence: 99%

Electron density profiles probed by radio occultation of FORMOSAT-7/COSMIC-2 at 520 and 800 km altitude

2015

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Abstract. The FORMOSAT-7/COSMIC-2 (F7/C2) will ultimately place 12 satellites in orbit with two launches with 24-28.5 • inclination and 520-550 km altitude in 2016 and with 72 • inclination and 720-750 km altitude in 2018. It would be very useful for the community to construct the global three-dimensional electron density structure by simultaneously combining the two launch observations for studying ionospheric structure and dynamics. However, to properly construct the global electron density structure, it is essential to know and evaluate differences between the ionospheric electron densities probed by the two launches. To mimic the F7/C2 observations, we examine the electron density probed at the two satellite altitudes 500 and 800 km by means of FORMOSAT-3/COSMIC (F3/C) observations at the parking orbit 500 km altitude and mission orbit 800 km altitude, as well as a corresponding observing system simulation experiment (OSSE). Observation and OSSE results show that the sounding geometries by satellite orbiting at 500 and 800 km altitudes can cause the overall differences in the electron density, the F2 peak electron density, and the F2 peak height of about 18-24, 12-28 %, and 7-19 km, respectively. Results confirm that the discrepancies mainly result from the sounding geometry and the grid (contour) bias of the electron density.

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“…Though the two-dimensional ionospheric tomography has been studied extensively from both the theoretical and observational aspects [5][6][7], in these studies only the ionospheric structure within a cross-section defined by the satellite orbit and the ground receiver array can be obtained, which limits strongly the observation time and place. In order to cope with the problem methods for author's e-mail: takeda-t@gakushikai.jp the three-dimensional CIT are being studied intensively by many authors [8][9][10][11][12][13][14]. In these analyses, usually, TEC data obtained for the ray paths between the Global Positioning System (GPS) satellites and ground receivers are used and to attain higher resolution sometimes the occultation measurement by the Low Earth Orbit (LEO) satellite is incorporated.…”

Section: Computerized Ionospheric Tomographymentioning

confidence: 99%

Ionospheric Tomography by Neural Network Collocation Method

Takeda

2007

Plasma and Fusion Research

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We describe a neural network collocation method (NNCM) for tomographic image reconstruction with small amount of projection data, which has been successfully applied to the three-dimensional ionospheric tomography based on the dataset of signal delays from the GPS satellites. In NNCM the neural network is trained by minimizing an object function composed of squared residuals of the governing equations evaluated at the collocation points and some constraining conditions imposed usually by observation data. This method is applied not only to the computerized tomography but also to the analyses of various inverse problems such as the data assimilation, the parameter estimation, the time series prediction, and so on.

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Ionospheric electron density profiles obtained with the Global Positioning System: Results from the GPS/MET experiment

Cited by 366 publications

References 14 publications

Enhanced E-layer ionization in the auroral zones observed by radio occultation measurements onboard CHAMP and Formosat-3/COSMIC

Enhanced E-layer ionization in the auroral zones observed by radio occultation measurements onboard CHAMP and Formosat-3/COSMIC

Electron density profiles probed by radio occultation of FORMOSAT-7/COSMIC-2 at 520 and 800 km altitude

Ionospheric Tomography by Neural Network Collocation Method

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