Impact of Solar Radio Flux on Ionospheric Phase Delay in GPS/LEO Occultation Methodology

The propagation of radio signal in the ionosphere is simulated based on the previous mathematical model.Given five data sets of real satellite state vectors from radio occultation measurements, the phase delays are respectively calculated with four different flux, i.e., flux=0,70, 160and240.It corresponds to four representative conditions, i.e.no solar activity, low solar activity, average solar activity and peak solar activity.The simulation has shown such features as follows:the ionospheric phase delay is obviously correlated with solar radio flux, and the greater solar radio flux, the greater ionospheric phase delay ;as for a rising occultation event, at the beginning, the phase delay increases, then it reaches a peak, finally it decreases till the end of occultation event.The phase delay differences among three different solar radio flux conditions tend to enlarge in the first most part of occultation event, however, they tend to narrow in the rest of the occultation event.Considering the strong correlation between the ionospheric phase delay and the solar radio flux, GPS radio occultation methodology is expected to contribute much to the study of solar and terrestrial relationship.