Wednesday, 20 October 2004

Where Have All the Sunspots Gone?

From NASA :
Solar physicist David Hathaway has been checking the sun every day since 1998, and every day for six years there have been sunspots. Sunspots are planet-sized "islands" on the surface of the sun. They are dark, cool, powerfully magnetized, and fleeting: a typical sunspot lasts only a few days or weeks before it breaks up. As soon as one disappears, however, another emerges to take its place.

Even during the lowest ebb of solar activity, you can usually find one or two spots on the sun. But when Hathaway looked on Jan. 28, 2004, there were none. The sun was utterly blank.

It happened again last week, twice, on Oct. 11th and 12th. There were no sunspots.

"This is a sign," says Hathaway, "that the solar minimum is coming, and it's coming sooner than we expected."
"Contrary to popular belief," says Hathaway, "the solar cycle is not precisely 11 years long." Its length, measured from minimum to minimum, varies: "The shortest cycles are 9 years, and the longest ones are about 14 years." What makes a cycle long or short? Researchers aren't sure. "We won't even know if the current cycle is long or short--until it's over," he says.

But researchers are making progress. Hathaway and colleague Bob Wilson, both working at NASA's Marshall Space Flight Center, believe they've found a simple way to predict the date of the next solar minimum. "We examined data from the last 8 solar cycles and discovered that Solar Min follows the first spotless day after Solar Max by 34 months," explains Hathaway.

The most recent solar maximum was in late 2000. The first spotless day after that was Jan 28, 2004. So, using Hathaway and Wilson's simple rule, solar minimum should arrive in late 2006. That's about a year earlier than previously thought.

The next solar maximum might come early, too, says Hathaway. "Solar activity intensifies rapidly after solar minimum. In recent cycles, Solar Max has followed Solar Min by just 4 years." Do the math: 2006 + 4 years = 2010
So what's the big deal? Well, the Sun is actually an unusually variable star for one of its size and position in the main sequence. Solar output affects cloud formation, and climate generally. Rather more so than the amount of Greenhouse gasses in the atmosphere.
Places now in drought can expect relief: and places that had unusual lulls in storm activity can now expect a more normal - and less pleasant - climate. At least for the next 4 years or so.

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