Space Weather Forecast: More Solar Storms on the Way

John Roach
for National Geographic News
January 9, 2008
The appearance last Friday of a lone dark spot on the sun signals that a new 11-year cycle of heightened solar activity is on the horizon, experts said.

Solar storms can knock out power grids, shut down satellite communications, and expose spacewalking astronauts to harmful radiation.

"We can now expect to see an increasing number of sunspots from [this new] cycle," said Douglas Biesecker, a solar physicist with the U.S. government's Space Weather Prediction Center in Boulder, Colorado.

Sunspots mark where a region of intense magnetic field from deep inside the sun emerges on its surface. The spots alone do not cause so-called space weather, but they are related to solar storms. More sunspots mean more stormy space weather.

The spots occur in cycles of increasing and decreasing activity that last approximately 11 years.

The last phase of heightened activity, dubbed Solar Cycle 23, peaked in 2000. The sunspot observed high in the sun's northern hemisphere on January 3 is the first definitely associated with Cycle 24, Biesecker explained.

"Seeing the first sunspot of the next solar cycle is important because it does mean that finally we're seeing what will be the eventual end of Cycle 23," he said.

For accounting purposes, Cycle 24 officially begins when the number of spots associated with it outnumbers the sunspots associated with Cycle 23, he added. That should occur within months.

David Hathaway is a solar physicist with the NASA Marshall Space Flight Center in Huntsville, Alabama. He equated last week's sunspot to the first kernel in a batch of popcorn going off.

"It takes them going off repeatedly before the new cycle takes over," he said.

What to Expect

Highly charged material ejected from the sun during solar storms causes power outages and disrupts satellite communications that can affect everything from taking cash out of an ATM to chatting on a cell phone.

In addition, this solar cycle will be the first to occur in an era when global positioning system, or GPS, technology is widely used, Biesecker noted.

"Many of those applications are of a precision that really does require knowledge of the space environment," he said.

For example, survey crews routinely use GPS to plot out the routes of new roads. Biesecker has heard reports of roads laid down during a solar storm that had to be relaid because of bad coordinates.

"GPS users need to be aware when they are getting errors in their GPS reading and when it is OK for them to go out and do the surveying," he said.

Hathaway noted that people who manage communications and power grid technology need to monitor the solar weather closely, but the general public need not worry too much.

"If the solar cycle had detrimental effects to our lives, we probably wouldn't be here," he said.

Frequency and Intensity

Space weather experts are evenly split over predictions of whether Solar Cycle 24 will be more or less stormy than average.

Hathaway said the predictions are primarily based on two different models, one estimating 140 to 150 sunspots per day at the cycle's maximum and the other about 75 to 80. The average is about 115 spots at maximum.

Within about two years after the minimum point of Solar Cycle 23, which is expected this spring, the solar activity will indicate which model was more correct.

"We're actively looking at those models and trying to figure out which one of these is right before the sun tells us," Hathaway said.

But whether the cycle is smaller or larger than average, Biesecker noted the distinction only applies to the number of storms, not the intensity of the storms.

"There's no correlation between storm intensity and the size of the solar cycle. It's just the number of storms you can expect," he said.

Another debate centers on what effect the solar cycle has on Earth's climate.

While there is some effect on stratospheric chemistry and ozone levels, Biesecker said it is likely minor.

"It isn't going to have a long-term climate effect," he said.

Hathaway noted that most solar scientists believe the sun is responsible for 20 to 30 percent of the temperature increase seen through the middle of the 20th century, though a few scientists argue that the sun has played a greater role.

(Read related story: "Sun Not a Global Warming Culprit, Study Says" [July 12, 2007].)

"We don't understand exactly what the connections are," he said.

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