14:45 〜 15:00
[MIS08-11] Detecting the ionospheric disturbances in Japan using the three-dimensional computerized tomography
キーワード：Computerized Ionospheric Tomography、Total Electron Content、Plasma Depletion、Medium-scale Traveling Ionospheric Disturbance
To reconstruct the 3-D structures related to ionospheric irregularities in Japan, the improved constraint least-square fitting algorithm was adopted. Unlike the conventional least-square fitting, spatial restrictions in horizontal direction were removed for better reproducing the disturbances. Before the performance on imaging ionospheric irregularities was evaluated, common assessments for quiet ionospheric conditions were first implemented. Taking the day of March 22, 2012, as an example, the results indicated that the characteristics of IED could be well retrieved by the improved algorithm. Then, the temporal and spatial IEDs related to plasma depletions and MSTIDs were elaborated, respectively. Especially for the storm-time depletion occurred on July 27, 2004, although it exhibited equatorward propagating characteristic, considering the abrupt fracture of up to 15 TECU imaged by TEC mapping, we speculated it was the abnormal PBs generated by the combing effects from the equatorward TADs and eastward PPEF during an intense storm. However, whether such irregularities being related to PBs or storm-induced LSTIDs is still worth further study and discussion in the future work. Next, Ne reconstruction for the nighttime MSTIDs on June 23, 2012, was conducted. The upward and downward motions of Ne were found to be connected with the negative and positive disturbances. Moreover, the sinusoidal structure concerning such disturbances indicates that an east-west oscillating EF exists in F region, then drives the plasma drift via δE × B. It is suggested that the electrodynamic process, as expected from the Perkins instability, plays an important role in generating the nighttime MSTIDs.