Vertical structure of medium‐scale traveling ionospheric disturbances

Abstract

We develop an algorithm of computerized ionospheric tomography (CIT) to infer information on the vertical and horizontal structuring of electron density during nighttime medium‐scale traveling ionospheric disturbances (MSTIDs). To facilitate digital CIT we have adopted total electron contents (TEC) from a dense Global Positioning System (GPS) receiver network, GEONET, which contains more than 1000 receivers. A multiplicative algebraic reconstruction technique was utilized with a calibrated IRI‐2012 model as an initial solution. The reconstructed F2 peak layer varied in altitude with average peak‐to‐peak amplitude of ~52 km. In addition, the F2 peak layer anticorrelated with TEC variations. This feature supports a theory in which nighttime MSTID is composed of oscillating electric fields due to conductivity variations. Moreover, reconstructed TEC variations over two stations were reasonably close to variations directly derived from the measured TEC data set. Our tomographic analysis may thus help understand three‐dimensional structure of MSTIDs in a quantitative way.

Real-Time Ionosphere Monitoring by Three-Dimensional Tomography over Japan

“…Recently, several studies have attempted three‐dimensional ionospheric tomography with GEONET data . The ionospheric tomography technique has evolved in reconstructing three‐dimensional ionospheric density distributions using a constrained least squares method with optimized constraining parameters .…”

Medium-scale traveling ionospheric disturbances by three-dimensional ionospheric GPS tomography

“…Because of the lack of horizontal GPS-TEC observation paths and incomplete path length matrix (aforementioned A matrix), the previous ionospheric tomography (Austen et al 1986) and multiplicative algebraic reconstruction technique (MART) (Raymund et al 1990;Ssessanga et al 2015), usually use the iteration method with an initial guess value to reconstruct the structure of the ionospheric electron density. These iteration methods are a mathematical procedure that generates a sequence of improving approximate solutions for the inverse problems.…”

“…The other problem is the lack of observations at the higher altitude region resulting in numerous areas that have no LOS ray passing through. Therefore, scientists employ an iterative method with an initial guess value from the ionospheric model, such as the international reference ionosphere (IRI) model, to approach the true solution of ionospheric electron density (Raymund 1995;Bilitza and Reinisch 2008;Ssessanga et al 2015). As a result, the solutions might be sensitive to the initial guess.…”

Tomography Reconstruction of Ionospheric Electron Density with Empirical Orthonormal Functions Using Korea GNSS Network

“…As an empirical model, IRI strongly depends on observed data sets, but has merits of fast computation as well as independence of heuristic theories. Therefore, IRI has provided an initial condition or reference values of ionospheric models and other applications, including the CIT reconstruction (Huang et al 1996;Arikan et al 2007;Ssessanga et al 2015). The latest IRI, IRI-2016 which was released in Feb. 2016, utilizes the hmF2 model based on constellation observing system for meteorology, ionosphere, and climate (COSMIC) developed by Shubin 2015, as an update from IRI-2012 (Bilitza et al 2016).…”

“…The elements of the geometry matrix for GPS rays can be computed with the subtendin the entry and exit points through a voxel in spherical geometry, where the angle is defined between tw emanating from the center of the Earth. Each GPS ray determines a plane that a receiver and a GPS (2) where m is total number of voxels, a ij indicates a length along which i-th GPS ray passes through j-th voxel, x j is the electron density at j-th voxel and e i is the error of measurement and approximation (Das & Shukla 2011;Ssessanga et al 2015). The matrix, a ij , is commonly called as a geometry matrix since it contains geometric information on the rays for the defined voxels.…”