Three-Step Tomographic Algorithm for Ionospheric Electron Density Reconstruction

In this work, a three-step algorithm for the tomographic reconstruction of ionospheric electron density (IED) is proposed. In the new algorithm, the Taylor series expansion of the multiplicative algebraic reconstruction technique is first introduced to perform an adaptive adjustment for the relaxation parameter vector. Second, the horizontal and vertical constraints are imposed on the tomography system aiming to reduce the dependence on the initial iteration values for those voxels without any rays traversing them. Third, the uniformed voxel size is replaced with the variable voxel size by adopting the unequal grid interval in the altitudinal direction. The feasibility and superiority of the three-step algorithm are validated by devising a numerical simulation scheme. Finally, the new algorithm is successfully used to obtain the 3-D IED distribution under magnetically quiet conditions. The comparisons of IED profiles and the statistics of the reconstruction error of different algorithms further validate the superiority of the three-step algorithm.