One large coronal mass ejection (CME) occurred in the Sun at 1642UT, Apr. 4, 2000. At about 1600 UT, Apr, 6, the high speed solar wind was detected by ACE satellite, the speed of which increased suddenly from 380 km/s up to 600 km/s. Then a southwards interplanetary magnetic field that lasts for 7 hours was observed. The solar wind push magnetosphere, and a large magnetic storm happened near the earth. At 0000 UT, Apr. 7, 2000, the Kp index reaches 8 and lasts for 6 hours. The minimum Dst index is -318 nT. During the magnetic storm, an ionospheric storm was also happened over the region of China shown by the observations of the ionosondes. Combining the temporal ionospheric TEC curves and the curves of the corresponding sub-ionospheric point derived from GPS measurements observed at Beijing, Wulumuqi, and Wuhan GPS stations, the morphology of ionospheric TEC over the region of 30°N-45°N and 85°E-120°E during the magnetic storm occurred on April 6-8, 2000 is studied. The results showed that, a weak negative storm over this region happened between 0200 BT and 0700 BT on April 7, 2000. Compared with the TEC on April 6, the largest value of TEC change is -8TECU. After 0800 BT, a strong ionospheric negative storm appeared over higher latitude region and became stronger and stronger with time. Meanwhile, an ionospheric positive storm developed over lower latitude region between 0700 BT and 0900 BT. During this period, the negative storm over higher latitude became gradually stronger, and moved southwards. Nevertheless the positive storm over lower latitude experienced an enhancing and declining process.
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