he sun's temper ebbs and flows on what scientists had thought was a pretty predictable cycle, but lately our closest star has been acting up.

Typically, a few stormy years would knock out a satellite or two and maybe trip a power grid on Earth. Then a few years of quiet, and then back to the bad behavior. But an extremely long stretch of low activity in recent years has scientists baffled and scrambling for better forecasting models.

An expected minimum of solar activity, between 2008 and 2009, was unusually deep. And while the sun would normally ramp up activity by now, heading into its next cycle, the sun may be on the verge of a weak solar cycle instead, astronomers said at the 216th meeting of the American Astronomical Society in Miami last month.

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"We're witnessing something unlike anything we've seen in 100 years," said David Hathaway of NASA's Marshall Space Flight Center in Huntsville, Ala.

The sun's constant interaction with Earth makes it important for solar physicists to keep track of solar activity. Stormy periods can force special safety precautions by satellite operators and power grid managers, and astronauts can be put at risk from bursts of radiation spat out by solar storm. Scientists need to more reliably predict what's in store.