Three‐Dimensional Reconstruction of Tongue of Ionization During the 11 October 2010 Geomagnetic Storm and Evolution Analysis With TIEGCM

Abstract The three‐dimensional computerized ionospheric tomography (3DCIT) technique that fused multisource data is used to reconstruct the spatial distribution of tongue of ionization (TOI) appeared over Greenland during a moderate geomagnetic storm on 11 October 2010. The reconstruction results are validated with observations from the constellation observing system for meteorology, ionosphere, and climate radio occultations and two ionosonde stations, which show good agreements. The 3DCIT images indicated a zone of high electron density (magnitude of ∼5 TECU) that crossed northern Greenland and electrons were input into the polar region in the anti‐sunward direction after aggregating at midlatitudes, which formed a TOI. The images also revealed that the TOI magnitude was larger in the upper ionosphere ssand lower at 300 and 500 km but still noticeable. Below 300 km, the TOI was difficult to detect. The simulation result of the Thermosphere‐Ionosphere‐Electrodynamic General Circulation Model (TIEGCM) also showed the same TOI structure. Then, we combined the measured ionospheric data and term‐by‐term analysis of the ion continuity formula in TIEGCM to further identify the principal TOI formation mechanisms. We assume that the dominant TOI formation mechanism is electric field transport, which is offset by ambipolar diffusion and neutral wind transport. Furthermore, the uplift of electrons and the insignificant effect of other physical processes explained the insignificant TOI in lower ionosphere.