engleski

Ionospheric disturbance evolution in equatorial area

Ionospheric delay is a major error source in Global Navigation Satellite Systems (GNSS) positioning. It is predominantly emphasised in periods of increased solar activity, when changes in the interplanetary magnetic field influence the geomagnetic field and cause significant disturbances in the ionosphere. The ionospheric activity in low latitudes is very complex, with highly variable ionization levels causing the phenomenon known as ionospheric scintillation. A number of ionospheric models have been developed in order to tackle the impact of the ionospheric delay on GNSS positioning accuracy. Even though the ionospheric models describe the ionospheric long-term behaviour very well, due to the complexity of fluid dynamics, chemical element distribution and interaction with the geomagnetic field, they still have to be improved to better describe local irregularities and fast developing ionospheric disturbances, even in quiet conditions. This paper will analyse ionospheric Total Electron Content (TEC) and its gradients in low latitudes during disturbed ionospheric conditions. Areas with the same geomagnetic latitudes will be compared in the same local time in order to monitor the development of the disturbance. In ideal situation where GNSS stations would be distributed all around the globe, disturbance evolution over time could be monitored. As such ideal receiver distribution is not available, monitoring of ionosphere is possible only in periods when the land mass with high receiver concentration reaches the targeted local time. Those areas include parts of Africa and South America and results will be focused on event in the descending phase of the solar cycle 24. Networks of GNSS stations provide empiric data used for monitoring of ionosphere and enable insight in spatial and temporal ionospheric gradients that could significantly influence GNSS performance and increase the positioning error. Ionospheric irregularities and gradients will be observed using calibrated vertical TEC data and TEC rate of change (ROT). Measured and calculated values will be interpolated over the observed geographical area using natural neighbour method and presented graphically, as well as numerically.

ionosphere, Total Electron Content, ionospheric gradients, scintillation, GNSS

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