Sun's face virtually spot-free for months

For the last eight months, the sunspots that usually freckle the Sun have virtually disappeared, and nobody knows when they'll return, or how plentiful they'll be. The speed at which the next breakout of spots occurs should reveal how active – and potentially damaging to Earth's satellites and power grids – the new solar cycle will be.

Sunspots are cooler, darker regions caused by the Sun's magnetic field ripping through the star's surface. They vary in number – going from a minimum to a maximum and back to a minimum again – about every 11 years, the same timescale on which the Sun's magnetic poles reverse direction.

Several dozen sunspots can appear every day during periods of maximum solar activity. But only a small handful of sunspots have occurred during all of 2008 to date, suggesting the Sun's activity is now at a minimum.

For a while, it even seemed like August would mark the first time since 1913 that no sunspots were seen for an entire month, according to record-keepers at the National Oceanic and Atmospheric Administration.

But when the final tally was made by the international authority on sunspots, the Solar Influences Data Analysis Center in Brussels, Belgium, one dark blip on 21 and 22 August was large enough to make the count.

Until the spots reappear, researchers say they will not know whether this 11-year solar cycle will bring heavier- or lighter-than-normal activity, or be able to resolve a raging debate about the mechanisms driving solar weather.

Anaemic cycle?

The current absence of sunspots does not necessarily foretell an anaemic cycle of solar activity to come, Leif Svalgaard of Stanford University says. Instead, sunspot watchers are waiting to see how fast the sunspot count starts to climb once they do reappear.

The quicker they return, the more active the solar weather will be for the following decade. "The big [cycles], they start out with a bang. One month, there may be none, the next month they may be all over the place," Svalgaard told New Scientist.

Some space meteorologists predict that the new cycle will be relatively quiet.

The prediction is based on theories suggesting magnetic fields that sink into the Sun near its poles are transported relatively quickly back to the Sun's surface, where they produce sunspots. Since observations show low magnetic field activity at the poles, the idea is that the coming solar cycle will be unspectacular.

'Worst nightmare'

Others theorise that magnetic fields travel for decades deep within the Sun's interior before returning to punch holes in its surface, creating sunspots. These forecasters predict that a strong wave of sunspots is right around the corner.

"As scientists, we're anxiously awaiting [the return of sunspots] because this is really going to help us weed out our different theories," says David Hathaway of NASA's Marshall Space Flight Center in Huntsville, Alabama.

"The worst nightmare is that it's right smack in the middle," Svalgaard says of the sunspots' rate of return. "Then all we know is [the models] are all bad."

Either way, the ramifications could be immense. Periods of strong solar magnetic activity and plentiful sunspots can interrupt communications and overload electricity grids on Earth.

Lengthy periods of low sunspot activity, on the other hand, such as the one between 1645 and 1715 called the Maunder Minimum, have been associated with cooler climate. What's to come in this case? We'll have to wait and see.