Simulation studies on the tomographic reconstruction of the equatorial and low-latitude ionosphere in the context of the Indian tomography experiment: CRABEX

摘要

Equatorial ionosphere poses a challenge to any algorithm that is used fortomographic reconstruction because of the phenomena like the EquatorialIonization Anomaly (EIA) and Equatorial Spread F (ESF). Any tomographicreconstruction of ionospheric density distributions in the equatorial regionis not acceptable if it does not image these phenomena, which exhibit largespatial and temporal variability, to a reasonable accuracy. The accuracy ofthe reconstructed image generally depends on many factors, such as thesatellite-receiver configuration, the ray path modelling, grid intersectionsand finally, the reconstruction algorithm. The present simulation study isperformed to examine these in the context of the operational Coherent RadioBeacon Experiment (CRABEX) network just commenced in India. The feasibilityof using this network for the studies of the equatorial and low-latitudeionosphere over Indian longitudes has been investigated through simulations.The electron density distributions that are characteristic of EIA and ESFare fed into various simulations and the reconstructed tomograms areinvestigated in terms of their reproducing capabilities. It is seen that,with the present receiver chain existing from 8.5° N to 34° N, itwould be possible to obtain accurate images of EIA and the plasma bubbles. TheSingular Value Decomposition (SVD) algorithm has been used for the inversionprocedure in this study. As is known, by the very nature of ionospherictomography experiments, the received data contain various kinds of errors,like the measurement and discretization errors. The sensitivity of theinversion algorithm, SVD in the present case, to these errors has also beeninvestigated and quantified.