Abstract
Abstract. Equatorial ionosphere poses a challenge to any algorithm that is used for tomographic reconstruction because of the phenomena like the Equatorial Ionization Anomaly (EIA) and Equatorial Spread F (ESF). Any tomographic reconstruction of ionospheric density distributions in the equatorial region is not acceptable if it does not image these phenomena, which exhibit large spatial and temporal variability, to a reasonable accuracy. The accuracy of the reconstructed image generally depends on many factors, such as the satellite-receiver configuration, the ray path modelling, grid intersections and finally, the reconstruction algorithm. The present simulation study is performed to examine these in the context of the operational Coherent Radio Beacon Experiment (CRABEX) network just commenced in India. The feasibility of using this network for the studies of the equatorial and low-latitude ionosphere over Indian longitudes has been investigated through simulations. The electron density distributions that are characteristic of EIA and ESF are fed into various simulations and the reconstructed tomograms are investigated in terms of their reproducing capabilities. It is seen that, with the present receiver chain existing from 8.5° N to 34° N, it would be possible to obtain accurate images of EIA and the plasma bubbles. The Singular Value Decomposition (SVD) algorithm has been used for the inversion procedure in this study. As is known, by the very nature of ionospheric tomography experiments, the received data contain various kinds of errors, like the measurement and discretization errors. The sensitivity of the inversion algorithm, SVD in the present case, to these errors has also been investigated and quantified.
Highlights
The basic idea of tomographic methods, which uses the line integral measurements through a field to reconstruct the field itself, was originated by Radon in 1917 and the first practical application seems to have been published by Bracewell (1956)
Austen et al (1988) suggested that using the total electron content (TEC), the tomography technique can be used for the two-dimensional imaging of electron density distribution in the ionosphere
An extensive feasibility study using known theoretical/ model generated electron density distributions is extremely useful in optimizing the receiver chain, to give reliable ionospheric images, especially when the region of interest is replete with large-scale ionospheric processes, like the Equatorial Ionization Anomaly and Equatorial Spread F
Summary
The basic idea of tomographic methods, which uses the line integral measurements through a field to reconstruct the field itself, was originated by Radon in 1917 and the first practical application seems to have been published by Bracewell (1956). As a fundamental principle in inversion problems, there is a direct relationship between the information contained in the measured data and the accuracy of the reconstructed image (Na et al, 1995) This means that the proper choice of the locations of the receiving stations, which could optimize the information content in a given latitudinal plane is one of the key factors for obtaining accurate images from any ionospheric tomography network. An extensive feasibility study using known theoretical/ model generated electron density distributions is extremely useful in optimizing the receiver chain, to give reliable ionospheric images, especially when the region of interest is replete with large-scale ionospheric processes, like the Equatorial Ionization Anomaly and Equatorial Spread F. Tomographic images obtained using CRABEX data will be presented in the future
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