Chapter 22 - The Effect of Solar Radio Bursts on GNSS Signals

Abstract

A solar radio burst (SRB) is the intense solar radio emission related to a solar flare and one of the extreme space weather events. If an SRB occurs with the enhancement in L band radio flux, it could influence the Global Navigation Satellite System (GNSS) signals through direct radio wave interferences. An SRB could result in reduction of signal-to-noise ratio (SNR) and instantaneous or long-period loss of lock (LOL) on GNSS signals. Therefore decreasing the observation quality, which subsequently will influence all the applications based on these observations such as radio occultation technique and precise GNSS positioning. An SRB will mainly affect stations located in the sunlit hemisphere during radio flux enhancement, while the strength of the influence depends on the solar incidence angle, the antenna pattern, the tracking algorithm, and some other factors. The threshold value of SRB flux value that could result in a significant effect on GNSS signals is believed to be between 1000–10,000 solar flux units (SFU; 1 SFU=10−22Wm−2Hz−1) in L band. Significant SRBs can occur at solar minimum and maximum. During 2003–12, eight SRB events occurred that have shown degrading effects on GNSS signals in the literature, which is approximately 8.8 events per solar cycle. Although the occurrence ratio is not significantly high, we should pay sufficient attention to its side effects on modern society.