By Ron Cowen
When twisted magnetic fields on the sun snap and unleash their energy, it’s the most ostentatious fireworks that grab the headlines. Brilliant explosions in the sun’s outer atmosphere can send billion-ton clouds of charged particles speeding towards Earth, where they can short-circuit electrical power grids and cause large-scale blackouts. The sudden release of magnetic energy can also generate solar flares, which pour a torrent of ultraviolet light and X rays into space. Solar flares can disable satellites and harm space-walking astronauts.
But a subtler kind of solar explosion has often gone under the radar. It involves powerful bursts of radio waves that often accompany solar flares. At 2:30 p.m. EST on Dec. 6, 2006, about an hour after a moderately energetic flare erupted, the sun emitted the most powerful burst of radio waves ever recorded (to hear an audio file of the radio burst, click here). During a high-intensity blitz that lasted more than 10 minutes, the storm swamped the entire sunlit side of Earth with radio noise. Across North and South America and parts of the Pacific, it overwhelmed dozens of radio receivers linked to the Global Positioning System (GPS). The network of GPS satellites provides critical distance and time information for everything from airplane navigation to maintaining the critical alignment of oil rigs as they drill into the seafloor.