Abstract
In this study, we develop a three-dimensional ionospheric tomography with the ground-based global position system (GPS) total electron content observations. Because of the geometric limitation of GPS observation path, it is difficult to solve the ill-posed inverse problem for the ionospheric electron density. Different from methods given by pervious studies, we consider an algorithm combining the least-square method with a constraint condition, in which the gradient of electron density tends to be smooth in the horizontal direction and steep in the vicinity of the ionospheric F2 peak. This algorithm is designed to be independent of any ionospheric or plasmaspheric electron density models as the initial condition. An observation system simulation experiment method is applied to evaluate the performance of the GPS ionospheric tomography in detecting ionospheric electron density perturbation at the scale size of around 200 km in wavelength, such as the medium-scale traveling ionospheric disturbances.
Highlights
Since late 1980s, the satellite radio tomography method has been employed to study the ionospheric electron density structure
Results for ionosphere with medium-scale TID (MSTID) The traveling ionospheric disturbances (TIDs) are wavelike electron density disturbances that propagate through the ionosphere and cause wave-like total electron content (TEC) disturbances (Davies 1990; Kelley 2011) due to external energy input to the ionosphere and/or plasma instabilities
In order to evaluate whether the global position system (GPS) tomography algorithm in this paper could be employed to reconstruct the ionospheric perturbations, we attempt to reproduce the three-dimensional density structure of MSTID from the two-dimensional GPS-TEC observations over Japan by performing an observation system simulation experiment (OSSE)
Summary
Since late 1980s, the satellite radio tomography method has been employed to study the ionospheric electron density structure. Austen et al (1986, 1988) first proposed the ionospheric tomography technique and measured the ionospheric total electron content (TEC) along the line of sight (LOS) from naval navigational satellite system (NNSS) to the ground-based receivers. They further successfully reconstructed the two-dimensional image of the ionospheric electron density from the onedimensional TEC data by using the technique of computerized ionospheric tomography (CIT). Previous CIT studies usually used the high-rate NNSS observation data to reconstruct the ionospheric electron density structure (Raymund et al 1990; Kunitake et al 1995) This kind of low earth orbit (LEO) satellites normally has relatively high ground-track velocity. Due to the slow-moving ground tracks and high elevation angle of GPS satellite, the spatial distribution of GPS-TEC observation data is not enough to reconstruct the three-dimensional electron density structure if the
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