Tomographic imaging of the ionosphere over Japan by the modified truncated SVD method

A computerized tomography technique was applied to reconstruct two-dimensional electron density distributions from measurements of total electron content (TEC). We found that the modified truncated singular value decomposition (MTSVD) method, which is usually effective in ill-posed inversion problems, is effective in the ionospheric application. Furthermore, a main control parameter for a good reconstruction was examined by using several density distribution models, and the effects of noise in TEC and discretization error were also investigated. After the simulation study, the MTSVD method was applied to actual TEC data in a magnetically disturbed period. Total electron contents were observed, at four receiving stations covering a latitudinal range of 9.7 degrees with a longitudinal range of 2.2 degrees over Japan, by using signals transmitted from a Navy Navigational Satellite System (NNSS) satellite. The tomographic reconstruction revealed a large-scale structure of electron density in the disturbed ionosphere.