Two-dimensional mapping of the plasma density in the upper atmosphere with computerized ionospheric tomography (CIT)

Abstract

Tomographic imaging of the ionosphere is a recently developed technique that uses integrated measurements and computer reconstructions to determine electron densities. The integral of electron density along vertical or oblique paths is obtained with radio transmissions from low-earth-orbiting (LEO) satellite transmitters to a chain of receivers on the earth’s surface. Similar measurements along horizontal paths can be made using transmissions from Global Position System (GPS) navigation satellites to GPS receivers on LEO spacecraft. Also, the intensities of extreme ultraviolet (EUV) emissions can be measured with orbiting spectrometers. These intensities are directly related to the integral of the oxygen ion and electron densities along the instrument line of sight. Two-dimensional maps of the ionospheric plasma are produced by analyzing the combined radio and EUV data using computerized ionospheric tomography (CIT). Difficulties associated with CIT arise from the nonuniqueness of the reconstructions, owing to limited angle measurements or nonoptimal receiver location. Improvements in both reconstruction algorithms and CIT measurement systems are being implemented to overcome these difficulties. New imaging systems being developed employ CIT for large area mapping of the plasma densities in the ionosphere.

The Initial Results from the LITN of the FORMOSAT-3 TBB Program

“…equa to rial anom a lies. Mean while, we also plan to ex tend the dis tri bu tion of the new LITN north to Beijing and south to Pare-Pare be fore 2008 and com bine the TBB ground receiver data with the other two sen sors on the COS MIC beacon, GOX and TIP (Bernhardt et al 1998) in the fu ture to obtain more com plete ob ser va tions.…”

Radio tomographic imaging of sporadic-<i>E</i> layers during SEEK-2

“…The updated pixel values get additive corrections for ART, multiplicative corrections for MART and simultaneous updates for Simultaneous Iterative Reconstruction Technique (SIRT). Details of setting up these algebraic methods are given by Bernhardt et al [1998]. data from a satellite moving along a trajectory defined by points k 2 =0, 1, 2,. .…”

“…Overviews of computerized ionospheric tomography (CIT) are given by Bernhardt et al (1998) and Kunitsyn and Tereshchenko (2003). CIT divides the solution space into a finite set of orthogonal basis functions and forms a set of linear equations that relate the electron density for each basis function to the set of TEC measurements.…”

Similarity transformations for fitting of geophysical properties: Application to altitude profiles of upper atmospheric species

“…In addition, some form of regularization or a priori information is necessary to ensure smoothness of the retrieved density profile in the presence of noise; otherwise, these alternatives can be sufficiently flexible to "fit the noise" or to become computationally unstable. In some instances [e.g., Bernhardt et al, 1998], combining different types of coincident data might preclude the need for regularization. That topic is outside the scope of the present discussion.…”