Application of generalized singular value decomposition to ionospheric tomography

摘要

The electron density distribution of the low- and mid-latitude ionosphere hasbeen investigated by the computerized tomography technique using aGeneralized Singular Value Decomposition (GSVD) based algorithm. Modelionospheric total electron content (TEC) data obtained from theInternational Reference Ionosphere 2001 and slant relative TEC data measuredat a chain of three stations receiving transit satellite transmissions inAlaska, USA are used in this analysis. The issue of optimum efficiency ofthe GSVD algorithm in the reconstruction of ionospheric structures is beingaddressed through simulation of the equatorial ionization anomaly (EIA), inaddition to its application to investigate complicated ionospheric densityirregularities. Results show that the Generalized Cross Validation approachto find the regularization parameter and the corresponding solutiongives a very good reconstructed image of the low-latitude ionosphere and theEIA within it. Provided that some minimum norm is fulfilled, the GSVD solution isfound to be least affected by considerations, such as pixel size and numberof ray paths. The method has also been used to investigate the behaviour ofthe mid-latitude ionosphere under magnetically quiet and disturbedconditions.