The effect of 20 May 2012 annular solar eclipse on the ionosphere

The 20 May 2012 annular solar eclipse crossed the mid-latitude ionosphere of Southeast China, Taiwan, Japan, and America West. The total electron content (TEC) derived from ground-based GPS receivers and frequency shifts recorded by Doppler sounding systems in Taiwan are employed to monitor the eclipse signatures. We compare the two observations on the eclipse day and those recorded 1-5 days before to find the associated eclipse effects. Results show that Doppler shifts yield negative values after the first contact but positive values after the third contact. The TECs variations and their time rate of changes are used to observe simultaneous responses of the ionosphere plasma density and soft Doppler during the annular solar eclipse.