Visualization and Analysis of Ionospheric Irregularities by Onboard and GroundReceivers
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Abstract
Radio occultation (RO) is a remote sensing technique that exploits the refraction of electromagnetic signals in the atmosphere, allowing for their investigation across different layers. In the context of this study, the research was based on the refraction of signals emitted by GNSS (Global Navigation Satellite Systems) satellites and received by low-Earth orbit (LEO) satellites. This technique makes it possible to determine refractive indices, which, through
processing and inversion techniques, provide atmospheric parameters. The ionosphere, composed of ionized particles and free electrons, affects GNSS signals due to refraction proportional to the TEC (Total Electron Content). In the equatorial region, the ionosphere exhibits a significantly high TEC due to the Equatorial Ionization Anomaly. Certain
irregularities in this medium can also cause ionospheric scintillation, which affects the quality of GNSS signals. In Brazil, ground-based monitoring stations have been established to monitor ionospheric scintillation; these stations are equipped with GNSS receivers that record variations in the amplitude and phase of the signals. In this regard, the main objective of this study is to analyze radio occultation data using the S4 ionospheric scintillation index and to validate it using data from monitoring stations located in the equatorial region. The results of the RO-GNSS data analyses made it possible to visualize the behavior of ionospheric irregularities at both the regional and global levels. Furthermore, consistency with data from ground stations was observed. The mean RMSE values for S4 ranged from
0.028 to 0.066, while the mean relative error ranged from 35.67% to 46.65%. The smallest errors occurred at the POAL station, located at a mid-latitude, highlighting the influence of geographic location on scintillations.
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