The December 2006 X9 Flare and GPS Disruption

What happened

An X9.0 flare on December 5, 2006, followed by an X6.5 flare on December 6, produced a solar radio burst 10 times stronger than any previously recorded. The burst overwhelmed civilian GPS receivers across the sunlit hemisphere for roughly ten minutes — the first clearly documented case of solar activity degrading GPS on a wide scale, and a wake-up call for aviation and precision-agriculture users.