Editing Geomagnetic storm (section)

==== Navigation systems ====

[[Satellite navigation|Global navigation satellite systems (GNSS)]], and other navigation systems such as [[LORAN]] and the now-defunct [[Omega Navigation System|OMEGA]] are adversely affected when solar activity disrupts their signal propagation. The OMEGA system consisted of eight transmitters located throughout the world. Airplanes and ships used the very low frequency signals from these transmitters to determine their positions. During solar events and geomagnetic storms, the system gave navigators information that was inaccurate by as much as several miles. If navigators had been alerted that a proton event or geomagnetic storm was in progress, they could have switched to a backup system.

GNSS signals are affected when solar activity causes sudden variations in the density of the ionosphere, causing the satellite signals to [[Scintillation (astronomy)|scintillate]] (like a twinkling star). The scintillation of satellite signals during ionospheric disturbances is studied at [[High Frequency Active Auroral Research Program|HAARP]] during ionospheric modification experiments. It has also been studied at the [[Jicamarca Radio Observatory]].

One technology used to allow GNSS receivers to continue to operate in the presence of some confusing signals is [[Receiver Autonomous Integrity Monitoring]] (RAIM), used by GPS. However, RAIM is predicated on the assumption that a majority of the GPS constellation is operating properly, and so it is much less useful when the entire constellation is perturbed by global influences such as geomagnetic storms. Even if RAIM detects a loss of integrity in these cases, it may not be able to provide a useful, reliable signal.