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Intense Solar Flare Worries Scientists
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Space weather is largely driven by the sun and its 11-year cycle of increasing and decreasing magnetic activity -- which can become visible as sunspots at its greatest intensity, or solar maximum. The last maximum was in 2000, and they generally last three to five years.
During a maximum, the magnetic field that surrounds the sun is regularly pierced by flares and coronal mass ejections of energy in the form of ultraviolet light, X-rays, highly charged protons and a "stormy" solar wind.
Much of the energy is blocked by Earth's magnetic field, but some larger solar flares produce radio bursts like the one that pierced the atmosphere last year.
While scientists were surprised by the intensity of the December radio blast, they are keenly aware that much about space weather remains imperfectly understood or simply mysterious. They also say most of the space-weather-related problems likely to occur in the future will happen when powerful radiation and electromagnetic forces hit the thousands of satellites that orbit Earth.
Both the Air Force and NOAA have space-weather observatories, with telescopes situated around the world to keep the sun's surface and its flares continuously in view. NOAA's Space Environment Center, which puts out regular reports on space-weather dynamics and trends, is headquartered in Boulder, Colo.
Murtagh, a forecaster in that office, said because space-weather records go back only a few solar cycles, "we don't really have a good idea yet of the boundaries of what's possible."
He said if someone had asked him on Dec. 4 if a radio eruption of the size that reached Earth two days later was possible, he would have said no.
"So now," he said, "if I was asked if one might come that's five or 10 times more powerful than the December 6 event, I would have to say: 'It's possible. We really don't know.' "
