TEC variations in the Southeast Asian equatorial anomaly region during the magnetic storms using signal from GPS satellite

Total Electron Content (TEC) of the ionosphere over the Southeast Asian region has been derived from measurements obtained at GPS ground stations of the International GPS Service (IGS) and three GPS ground stations of Vietnam in 2010. This paper presents the results of the study of the TEC variations during four magnetic storms on 4-10 April, 1-9 May, 1-8 August and 10-15 October, 2010. It was found that the structure of the daytime equatorial ionization anomaly (EIA), which consists of two peaks in the vicinity of 10°-15° magnetic latitude. Results are also shown that both peaks are fully developed at around afternoon. The TEC values of peaks on 4-10 April and 10-15 October are higher than on 1-9 May and 1-8 August. During the early stage of the magnetic storms, the EIA expanded poleward with large increases of TEC, which provides evidence of a penetration of the eastward electric field and a strong plasma fountain effect associated with the upward plasma drifts. In the recovery phase, the EIA is significantly reduced; the TEC value decreases and the peaks move equatorward.