Study on the electronic density perturbation detected by DEMETER satellite before Wenchuan earthquake

We used slope analysis and sliding Median method to study the electron density data observed by Langmuir probe of DEMETER satellite since April 25, 2008 to May 11, 2008, and obvious perturbation phenomena of electron density(N_e) in ionosphere were found before Wenchuan earthquake on May 12, 2008. Considering the geomagnetic disturbances, there were some abnormal information in different degrees on May 3, 4, 7, 9, 10, 11 respectively. Furthermore, on May 3 and May 4, along with the change of electron density, electron temperature was also elevated at the latitude of 10~30°N. Also on May 7, not only electron density increased, but also ion density did above the epicentral area.