TEC and Scintillation observed over Ho Chi Minh, Vietnam during 2009-2012

The ionospheric total electron content (TEC) and scintillation (S4) over Ho Chi Minh City (HCM) was studied using the Global Positioning System (GPS). We analyzed GPS data during the recent solar cycle 24 from 2009 to 2012. Some results show that both TEC and scintillation in this area presented the seasonal variations peaking on the equinox months. The vertical TEC observed in HCM is high unusually in spring and autumn equinoxes of 2011 but they seem to agree with solar activity index. The scintillation statistics show that their occurrence is almost at night and the S4 index in this region do not exceed the value of 0.8. GPS TEC was using to compare with IRI-2012 model and found the big gap of TEC in 2011. In latest two years, the high solar activity with lots of flares and Coronal Mass Ejections (CMEs) were erupted. Two major geomagnetic storms in August 2011 and March 2012 were examined for seeing the changes of TEC and S4 in South Vietnam.