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Abstract
An empirical model of ionospheric electron content (IEC), based on FORMOSAT3/COSMIC (F3/C) data, is constructed in order to detect pre-earthquake anomalies. The empirical model provides IEC with four parameters of local time, season, longitude and latitude. For the first time we try to detect anomalies in the F3/C IEC by comparing the model values with observations during the 12 May 2008 Wenchuan Earthquake period. It is found that around the epicentre an IEC enhancement appears on day 3 (9 May) and sequential IEC reductions occur on day 6 to day 1 (6 to 11 May) before the earthquake.
Acknowledgment
The geomagnetic indices Dst, Kp, AU and AL were obtained from the World Data Center, Kyoto University, Kyoto, Japan. This research is partially supported by grants from the National Science Council NSC97-2116-M-008-013; the Central Weather Bureau MOTC-CWB-97-E-17, and the Ministry of Education 5y50b, the iSTEP project of the National Central University.