Equatorial ionospheric zonal drift by monitoring local GPS reference networks

The propagation of electromagnetic waves through the turbulent ionosphere produces scintillations through diffraction, and understanding the physical nature of scintillations is important for engineers and technologists as well as for scientists. In recent years, the establishment of the Global Positioning System (GPS) provided a new technique that can be used to study ionospheric scintillations. The usual way of doing that is the deployment of GPS receivers closely spaced in east-west magnetic direction and then estimating the zonal drift velocities based on the signal power observations. One of the weaknesses of this method is that high-rate sampling such as 20 Hz is required for close-spaced stations and generally no such data are available for studying ionospheric scintillation in the past years. In this research work, a scintillation monitoring method based on slant TEC (STEC) observations of local GPS Continuously Operating Reference Station (CORS) network is proposed. First, the past research works on the equatorial ionospheric drift velocities are summarized. Then, by comparing the scintillation pattern of the signal power and STEC observations of California local GPS reference network, we find that the STEC is a good choice for estimating the ionospheric zonal drift velocity. Then it is illustrated how to calculate the ionospheric scintillation velocity based on STEC. Finally, the proposed method is applied to Hong Kong GPS reference network and several cases of the calculated ionospheric zonal velocities are given.