A tomographic model for ionospheric imaging with the Global Ultraviolet Imager

Abstract

[1] A tomographic forward and inverse model is presented that enables the recovery of three-dimensional ionospheric structures from space-based optical observations. In this paper we apply the technique to the Global Ultraviolet Imager (GUVI) on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. The forward model is based on GUVI observation geometry to simulate radiance observations of a model ionosphere. This model incorporates the physics of the 1356 Å emission and the pattern of line-of-sight measurements out of the plane of the orbit into a discrete matrix representation of the GUVI observation. The application of matrix inversion techniques to the discrete observation matrix allows a multidimensional electron density profile to be reconstructed from the GUVI brightness measurements. Appropriate regularization functionals are incorporated to constrain the reconstructed solution. A smoothness constraint with a nonconvex penalty function ensures smoothness while preserving edges in the reconstructed image, an attribute which is crucial for the reconstruction of sharp ionospheric gradients. Results using GUVI data are shown to demonstrate the applicability of this technique.

The Far Ultra-Violet Imager on the Icon Mission

“…Ionospheric plasma bubbles seem to occur on one day but are completely absent on another seemingly under identical ionospheric conditions (Kamalabadi et al 2009). These bubbles were studied in the far ultraviolet (Comberiate et al 2007) using the GUVI instrument on TIMED. The ICON FUV instrument provides a new opportunity to image and study the bubbles and the associated ionospheric conditions.…”

Gravity wave and tidal influences on equatorial spread F based on observations during the Spread F Experiment (SpreadFEx)

“…The descending node of each TIMED orbit provides two views of the plasma depletions having a component normal to the magnetic field from which tomographic retrievals of electron densities may be performed (Kamalabadi et al, 1999(Kamalabadi et al, , 2002Comberiate et al, 2007). The major assumption was that electron density fluctuations were approximately constant along magnetic field lines.…”

Space-Based Three-Dimensional Imaging of Equatorial Plasma Bubbles: Advancing the Understanding of Ionospheric Density Depletions and Scintillation

“…The major source of error is the statistical error from the low number of photon counts in the observation. Comberiate [2007] presents an analysis of statistical error based on a Gaussian noise model. When there are insufficient counts (< 10 counts) to model the Poisson counting process as Gaussian, reconstructed electron density values may be biased high.…”

“…1. Details of the tomographic reconstruction algorithm are described in Comberiate et al [2007]. Additional cross-sections are reconstructed at 6.4° latitude intervals (five cross-track scans span 6.4° latitude), such that 12 slices are combined to form a three-dimensional electron density profile.…”

“…where y is an array of SSUSI 135.6 nm brightness measurements, x is an array of discrete ionospheric voxels with constant values for the squared electron density, and A is a matrix where the values A(i,j) are the lengths of the line of sight for observation i contained in the ionospheric voxel j [Comberiate et al, 2007]. The tomographic inversion algorithm is a method for solving for the unknown ionosphere x in Eq.…”