Irregular density variations in the ionosphere and motion of these irregularities can cause diffraction effects of trans-ionospheric radio signals. When received at an antenna, these signals present random temporal fluctuations in both amplitude and phase. This is known as ionospheric scintillation.
Ionospheric scintillation may cause problems such as singal power fading, phase cycle slips, receiver loss of lock, etc., and degrade the quality of satellite navigation systems. Being concerned about the effects, the National Space Weather Program (NSWP) lists ionospheric irregularities/scintillation as one key component of the space weather. The program requires systems capable of monitoring, nowcasting, and forecasting solar influences on Earth's space environment, including global activity of ionospheric irregularities and scintillation.
The current global GPS network contains about 360 GPS stations, and the number of stations is still increasing. Each receiver at these stations is capable of receiving L-band dual frequency signals from 8+ GPS satellites (totally 24) simultaneously in different directions. GPS data are downloaded to JPL through Internet and commercial phone lines on near real-time and daily bases. This network is a potential resource that can be used to achieve the NSWP goals.