Tomographic reconstruction of the ionospheric electron density as a function of space and time

Abstract

Electron density distribution is the major determining parameter of the ionosphere. Computerized Ionospheric Tomography (CIT) is a method to reconstruct ionospheric electron density image by computing Total Electron Content (TEC) values from the recorded Global Positioning Satellite System (GPS) signals. Due to the multi-scale variability of the ionosphere and inherent biases and errors in the computation of TEC, CIT constitutes an underdetermined ill-posed inverse problem. In this study, a novel Singular Value Decomposition (SVD) based CIT reconstruction technique is proposed for the imaging of electron density in both space (latitude, longitude, altitude) and time. The underlying model is obtained from International Reference Ionosphere (IRI) and the necessary measurements are obtained from earth based and satellite based GPS recordings. Based on the IRI-2007 model, a basis is formed by SVD for the required location and the time of interest. Selecting the first few basis vectors corresponding to the most significant singular values, the 3-D CIT is formulated as a weighted least squares estimation problem of the basis coefficients. By providing significant regularization to the tomographic inversion problem with limited projections, the proposed technique provides robust and reliable 3-D reconstructions of ionospheric electron density.

Performance of Solar Proxy Options of IRI‐Plas Model for Equinox Seasons

“…IONOLAB group has been using IRI‐Plas as a background ionosphere model in the development of various HF communication (Sezen et al, ), High Frequency (HF) ray tracing and propagation (Erdem & Arikan, ), Computerized Ionospheric Tomography (Erturk et al, ; Tuna et al, ), and 1‐D and 2‐D imaging (Arikan et al, ; Arikan, Shukurov, et al, ; Tuna et al, ) algorithms. IRI‐Plas has also been offered as an online Space Weather service at http://www.ionolab.org with a user‐friendly interface (Arikan, Sezen, et al, ; Sezen et al, ).…”

“…The most recent version of IRI includes two new model options for the peak ionization height of F2 layer, hmF2, and a revised representation of topside ion densities at very low and high solar activities . IONOLAB group has been using IRI-Plas as a background ionosphere model in the development of various HF communication (Sezen et al, 2013), High Frequency (HF) ray tracing and propagation (Erdem & Arikan, 2017), Computerized Ionospheric Tomography (Erturk et al, 2009;Tuna et al, 2015), and 1-D and 2-D imaging Arikan, Shukurov, et al, 2016;Tuna et al, 2014) algorithms. IRI-Plas has also been offered as an online Space Weather service at www.ionolab.org with a user-friendly interface (Arikan, Sezen, et al, 2016;Sezen et al, 2017).…”

Regional model‐based computerized ionospheric tomography using GPS measurements: IONOLAB‐CIT

“…Therefore, to overcome the issues of insufficient data, many methods use some kind of regularization together with a background ionosphere model such as those discussed in Fridman et al [2006] and Yao et al [2014]. Some CIT methods utilize basis functions for constraining the solution in a predetermined problem space as given in Arikan et al [2007b] and Erturk et al [2009]. Examples of model-free iterative approaches can be found in Lee et al [2008] and Wen et al [2008].…”

Spatio‐temporal interpolation of total electron content using a GPS network

“…Services in navigation, positioning, surveying, and monitoring of SW require continuous operation of GPS receivers and uninterrupted TEC estimation for 24 h. The continuous data sets are used in modeling of ionosphere, TEC mapping, computerized ionospheric tomography (CIT), within‐the‐hour statistical analysis, ionospheric earthquake precursor studies, and prediction of SW events such as those provided in Erturk et al . []; Karatay et al . []; Turel and Arikan , []; and Foster and Evans [].…”