Recently, it is found that the East‐Asian ionosphere was characterized by a strong westward gradient in maximum electron density of F2 layer (NmF2) and topside ion density (Ni) persisting over a day at both the bottomside and topside ionosphere at mid‐low latitudes during the main and recovery phases of the 13–14 March 1989 great magnetic storm. Their simulation results from the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) under Apex and Dipole geomagnetic fields illustrates that the model reproduces this strong zonal gradient better under realistic geomagnetic field model than dipole geomagnetic field. The conditions favor for this structure requires a hemispheric asymmetry response of storm thermosphere as well as background condition. Their work shows that in the East Asia region, The ionosphere over the eastern China and Japan would manifest totally different storm behaviors during the superstorm even at very close stations suggesting a great challenge in the space weather prediction. In this study, we continue this investigation by analyzing some other storm cases to find if this structure is unique or represents a type of ionospheric storm response in the East Asia region during the great magnetic storms. We have studied dozens of ionospheric storms during the 23th solar cycle and found two cases that quite similar to the event of the great 1989 storm. In the following sector, we are about to represent these data and by using the TIEGCM, a physical explanation is carried out to show how this structure is formed and how it is applied in predicting storm effect.
 

Ionospheric,longitude Difference,Magnetic Storm