Usability analysis of the amplitude scintillation index S_4c derived from BDS-3 observations

The third phase of BDS (BDS-3) began to provide fully global positioning service. To investigate the performance of BDS observations in ionospheric scintillation index establishment, this study focuses on the construction of amplitude scintillation index S-4c using the carrier-to-noise ratio data of BDS-3. Based on the newly installed ionospheric scintillation monitoring receiver (ISMR) data at the Ledong station in Hainan from July 2021 to December in 2022, the relationship between the amplitude scintillation indexes S-4c and S-4 is analyzed and compared. Statistical results indicate the correlation coefficient between S-4c and S-4 can reach 0.95. To analyze the magnitude difference of S-4c derived from different geodetic GNSS receivers, six groups of collocated stations at various latitudes are employed to calculate the S-4c from January to December in 2022. The values of S-4c processed by different types of receivers are slightly different, sorted by the processed values in descending order as TRIMBLE > LEICA > SEPTENTRIO, where the mean value of difference between TRIMBLE and SEPTENTRIO is about 0.05, and the mean value of difference between LEICA and SEPTENTRIO is about 0.03. The six collocated groups of stations showed a significant increase in the difference in S-4c values within the season of the year when scintillation occurred, with the increased values moving up and down in the range of one-fifth of the mean values. Finally, the S-4c is applied in detecting ionospheric irregularities during the Tonga volcanic eruption on January 15, 2022. It is found that the ionospheric irregularities start at 11:00 UT and drift westward from the eruption center region, gradually shifting to the Southeast Asia region with obvious scintillation.