5:15 PM - 7:15 PM
[MTT37-P10] Temporal Variation in 1-second TEC Data Derived from Ultra-Dense GNSS Observation Network
Keywords:Ionosphere, GNSS, Total Electron Content, Multipath
Total Electron Content (TEC) data derived from the Global Navigation Satellite System (GNSS) has become essential in ionospheric research in recent years. In Japan, the Geospatial Information Authority of Japan (GSI) has established the GNSS Earth Observation NETwork System (GEONET), which consists of approximately 1,300 GNSS reference stations nationwide. A pair of satellites and receivers produce one TEC data point, and a large amount of TEC data is being collected across Japan.
Recently, data from SoftBank Corporation's base stations have also been made available. Additionally, one-second resolution data is accessible, providing high-density and high-time-resolution datasets.
We have been analyzing ionospheric disturbances using one-second resolution TEC data. However, during the analysis, variations that were considered to be influenced by factors other than natural phenomena were observed. Analysis of TEC data obtained from observation points, mainly in the Kanto region, revealed periodic fluctuations in the frequency range of 0--100 mHz. Furthermore, these fluctuations exhibited a parabolic periodic variation with a period of six hours. The TEC data used in this study were derived using pseudorange measurements from two different frequencies. The parabolic variations discovered in this study are believed to be caused by multipath effects on the two-frequency radio waves. Additionally, a sudden broadband spectral increase was observed daily around 1:00 UT. Since this type of periodic fluctuation was found to occur or not, depending on the satellite's position relative to the same base station, it is considered an effect of multipath interference. When GNSS receivers are mounted on the sides of buildings rather than on protruding structures, such influences are likely to occur depending on the satellite's position.
The SoftBank's GNSS observation data used in this study was provided by SoftBank Corp. and ALES Corp. through the framework of the "Consortium to utilize the SoftBank original reference sites for Earth and Space Science".
Recently, data from SoftBank Corporation's base stations have also been made available. Additionally, one-second resolution data is accessible, providing high-density and high-time-resolution datasets.
We have been analyzing ionospheric disturbances using one-second resolution TEC data. However, during the analysis, variations that were considered to be influenced by factors other than natural phenomena were observed. Analysis of TEC data obtained from observation points, mainly in the Kanto region, revealed periodic fluctuations in the frequency range of 0--100 mHz. Furthermore, these fluctuations exhibited a parabolic periodic variation with a period of six hours. The TEC data used in this study were derived using pseudorange measurements from two different frequencies. The parabolic variations discovered in this study are believed to be caused by multipath effects on the two-frequency radio waves. Additionally, a sudden broadband spectral increase was observed daily around 1:00 UT. Since this type of periodic fluctuation was found to occur or not, depending on the satellite's position relative to the same base station, it is considered an effect of multipath interference. When GNSS receivers are mounted on the sides of buildings rather than on protruding structures, such influences are likely to occur depending on the satellite's position.
The SoftBank's GNSS observation data used in this study was provided by SoftBank Corp. and ALES Corp. through the framework of the "Consortium to utilize the SoftBank original reference sites for Earth and Space Science".