Imaging the Ionospheric Electron Density Usinga Combined Tomographic Algorithm

摘要

A new algorithm, which is the combination of therngeneralized singular value decomposition (GSVD) and thernimproved algebraic reconstruction technique (IART), isrnproposed to image ionospheric electron density （IED）rndistribution in this paper. In this new method, the GSVD isrnfirst used to resolve the ill-posed problem in computerizedrnionospheric tomography (CIT) system. Its estimate invertedrnfrom total electron content (TEC) measurements is thenrnprovided as the initial approximation required by the IART.rnThe combined algorithm therefore offers a more reasonablernapproach to choose an initial approximation for the IARTrnand improve the quality of the final reconstructed image. Arnnumerical simulation experiment demonstrates that therncombined algorithm is more accurate than the GSVD alonernor the IART alone for the tomographic inversion of IED. Thernnew method is then applied to perform the inversion of thernIED during a magnetically disturbed period on 21 Augustrn2003. Tomographic results show that the main ionosphericrneffects of this storm over China are as follows: the negativernstorm phase effect appears in F region, the positive stormrnphase effect occurs above F region, and meanwhile, somernprominent features in the ionospheric structure can bernrevealed in the ionospheric images, such as the disturbance and mid-latitude trough. The reliability of the new method isrnalso validated by the ionosonde data recorded at Wuhanrnstation.