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

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.

Two‐dimensional ionospheric tomography over the low‐latitude Indian region: An intercomparison of ART and MART algorithms

“…There is a direct relationship between the information contained in the measured TEC data and the accuracy of the reconstructed image. Thus the proper choice of receiving stations which could optimize the information contend in a given longitudinal plane is one of the key factors for obtaining accurate images from any ionospheric tomography network [ Thampi et al , 2004].…”

Tomographic imaging of the equatorial and low-latitude ionosphere over central-eastern Brazil

“…Ground-based ionospheric radio soundings and rockets are examples of instruments widely used to monitor the ionospheric electron density (see e.g. Abdu et al, 1990;Walker et al, 1991). Recently, with the availability of a signi cant amount of data sets from Global Navigation Satellite Systems (GNSS), integrated measurements of electron density, also known as total electron content (TEC), have also revealed important features of the equatorial anomaly.…”

“…At equatorial and low latitudes ionospheric imaging technique has provided relevant information on the vertical structure of the electron density, its temporal variation and how it is lifted up and transported to other regions. Moreover, tomographic imaging has been applied at different longitude sectors and contributed signi cantly in the understanding of the ionospheric dynamics in the equatorial anomaly region, its seasonal and day-to-day variability and response under different geomagnetic conditions (Huang et al, 1997;Andreeva et al, 2000;Kunitsyn et al, 2003;Thampi et al, 2004). In the South-American sector the rst attempt to reconstruct the ionosphere by using tomographic inversion technique is due to Pakula et al (1994).…”

First results from the ionospheric tomography experiment using beacon TEC data obtained by means of a network along a longitude of 136°E over Japan

“…In other words, the elements of A denote the length of a ray that passes through the pixels of interest. E represents the measurement and discretization errors (Thampi et al, 2004). Since this is a highly ill-posed inverse problem, several iterative as well as non-iterative algorithms are currently being used for the inversion.…”

“…Such observations from a chain of receivers (aligned along a meridian) are then inverted to obtain the electron density distribution as a function of latitude and altitude over a given longitude. A typical configuration used for ionospheric tomography, consisting of a LEOS and three ground-based receivers is shown in Thampi et al (2004). The region to be imaged is divided into pixels, and the electron density in each pixel is assumed to be a constant.…”