This study presents the continuous GPS network in Vietnam and the results of study on time variations of the total electron content (TEC) in the South East Asian equatorial ionization anomaly (EIA) for the 2006-2013 period. In each year we observe a semiannual pattern of amplitude of the EIA crests with its maximum amplitude at equinox. | Vietnam Journal of Earth Sciences, 38(2), 153-165, DOI: Vietnam Academy of Science and Technology Vietnam Journal of Earth Sciences (VAST) Continuous GPS network in Vietnam and results of study on the total electron content in the South East Asian region Le Huy Minh*1, Tran Thi Lan1, C. Amory-Mazaudier2, R. Fleury3, A. Bourdillon4, J. Hu5, Vu Tuan Hung5, Nguyen Chien Thang1, Le Truong Thanh1, Nguyen Ha Thanh1 1 Institute of Geophysics, VAST LPP/UPMC/Polytechnique/CNRS, UMR 7648, France 3 Lab-STICC UMR 6285 Mines-Télécom Télécom Bretagne, France 4 Institut d’Electronique et de Télécommunication, Université de Rennes, France 5 National Taiwan University, Republic of China 2 Received 19 January 2016. Accepted 27 April 2016 ABSTRACT This study presents the continuous GPS network in Vietnam and the results of study on time variations of the total electron content (TEC) in the South East Asian equatorial ionization anomaly (EIA) for the 2006-2013 period. In each year we observe a semiannual pattern of amplitude of the EIA crests with its maximum amplitude at equinox. In both hemispheres, the amplitude of the crest is larger in northern spring equinox than in autumn from 2006 to 2008 (descending phase of solar cycle) and smaller in spring than in autumn from 2009 to 2011 (increasing phase of solar cycle), from 2012-2013 (maximum period of solar cycle) the amplitudes of the crests in spring and autumn are equivalent. We also observe an asymmetry between the amplitude and the position of the two crests of ionization. There is a very high level of correlation between the amplitude of the TEC at the two crests and the sunspot number is approximately equal to . During the deep solar minimum 2008-2009, the amplitude of crests of ionization becomes small during several months in summer and winter (about 20 TECu). The results show that both crests move more significantly equatorward in winter than in other .
