Will the next solar cycle please stand up?

Posted by David Eicher
on Wednesday, December 13, 2006

Astronomers at the American Geophysical Union meeting in San Francisco are debating predictions of what the next solar cycle, number 24, which will start next year and will peak in 2011, will be like. Ironically, with new techniques to analyze solar cycles and with more observations than ever before, solar physicists are predicting a wider range of possibilities than ever before. As astronomer Bill Murtagh of NOAA's Space Environment Center says, "The next solar cycle might among the biggest ever, or extremely small. There are several schools of thought!"

Why does it matter? The level of solar activity affects satellite communications, the power grid, the airline industry's ability to fly polar routes and to keep passengers safe from radiation, deep space missions, GPS operations, the Space Station's viability, and climate change. Moreover, an extremely active next solar cycle could bring the Hubble Space Telescope down more quickly. So it's important for astronomers to be asking, "What kind of geomagnetic storms might we have over the coming cycle?"

Murtagh's colleague Dean Pesnell of NASA's Goddard Space Flight Center expects a mild solar cycle 24. Pesnell uses a measure of the Sun's polar magnetic field as an indicator and believes the coming cycle will be mild, with about 70 sunspots as an average seen on any given day. David Hathaway of NASA's Marshall Space Flight Center, on the other hand, uses a "listening" technique by which he monitors Earth's magnetic field for early signs of activity associated with the Sun's magnetic field. Hathaway predicts an extremely active solar cycle 24, with an average sunspot number more than twice as great as Pesnell's - one that should equal the second or third most active ever recorded.

NOAA's Doug Biesecker gets the unenviable task of producing a committee report by this coming April that will serve as the official prediction. Biesecker might be nicknamed the "Sun king." How does he anticipate reconciling all this? He has sunspot number predictions ranging from 42 to 185, and promises to take all the advice from everyone, and the wide-ranging methods like those of Pesnell and Hathaway, into account. One thing's for sure: the next solar cycle will be the most studied of all time, and it may well be the most active.

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