New observations of the total electron content and ionospheric scintillations over Ho Chi Minh city

In January 2018, a Trimble NetR9 GNSS receiver was installed at International University - Vietnam National University (IU-VNU), which is located at 10 degrees 52'N, 106 degrees 48'E in Ho Chi Minh City (HCMC). The GNSS signals recorded from ground-based receivers are useful for studying the ionospheric variations as well as the magnetosphere-ionosphere coupling effects, therefore, we aim to process and evaluate data recorded from this new station. Based on the obtained data, we first estimated the total electron content (TEC) using the carrier-phase method which is a combination of code and phase measurements. We then calculated the rate of change of TEC index (ROTI) with respect to time and investigated its day-to-day variations. Our results present typical features of diurnal and seasonal variations of TEC and ionospheric scintillation during 2018-2019. The distributions of ROTI over these two years of solar minimum show significant occurrences of scintillations, which are caused by small-scale ionospheric irregularities in the equatorial ionosphere. In addition, we found a significant increase of TEC in the latest strong geomagnetic storm in August 2018. The disturbance dynamo appears to have suppressed plasma bubbles after sunset and enhanced their formation at midnight. Thus, the disturbance dynamo effectively caused a delay of ionospheric scintillations. The TEC observed in HCMC also contributes to the data of ground-based observational receiver systems along 105 degrees E longitude for studying ionospheric variations in low-latitude and equatorial regions. Our preliminary results indicate that the GNSS data collected at IU-VNU station is a valuable reference dataset for further research.