Low sunspot cycle fascinates scientists, who say there's no reason to panic

Unusual trends — especially astronomical ones — are a great way to cause the public to panic.

But for those worried about a strangely long trend of missing sunspots, scientists have a message: Don't expect the sun to change its spots overnight.

Sunspots are dark areas on the sun's surface caused by intense magnetic activity. They indicate a natural sort of churning caused by the rotation of plasma inside the sun. And they are often associated with things like solar flares, mass ejections and other phenomenon indicating increased solar activity.

Since 2004, the sun has been in a prolonged period of low sunspot activity, which has led some to fear that the phenomenon could lead to global cooling, a new ice age, the death of the sun or even to the end of the world predicted by the Mayan calendar.

But the reality is that the phenomenon is part of a natural 11-year repeating sunspot cycle that fluctuates from intense activity to no activity and back again about every six years. And while it's interesting that the low number of sunspots over the past few years is the fourth longest such trend since the mid-1600s, it's by no means any reason to panic, said Geoff Reeves, a space scientist at Los Alamos National Laboratory.

"The sun is very quiet right now, and there's been a lot of discussion about how quiet that is, and how unusual that is," Reeves said. "My prediction is that yes, the number of sunspots will pop up again, at some point. That's a pretty safe prediction to make."

The low activity period we're in now is called the solar minimum, and so far in this cycle there have been 602 days — as of last Tuesday — without sunspots. In a typical solar minimum, there's an average of 485 days, Reeves said.

And the solar minimum, which some scientists predicted would end by September 2008, is still happening.

"We expect there will be more days with no sunspots while the activity starts to return and ramp up, and we could end up with a record number of days in this solar minimum," Reeves said.

Solar minimums haven't been studied very much, he added. The longest one, called the Maunder minimum, happened between 1645 and 1715, when the sun appeared to miss a whole cycle. During that time, only about 50 sunspots were observed.

That period also correlates with the Little Ice Age, which started in 1650 and ended in the mid-1800s. That cold period caused rivers to freeze all over Europe and in the eastern United States, and resulted in the growth of glaciers in those areas.

The connection between those two events is poorly understood. But there is some evidence that a lack of sunspots can cause moderate cooling because of the way the sun interacts with Earth's outer atmosphere, said Alexei Pevtsov, staff astronomer at the National Solar Observatory in Sunspot, N.M.

When solar activity is high, sunspots, flares and other phenomenon can disrupt satellite communications and swell the upper boundary of the Earth's ionosphere, its topmost atmospheric level. But high activity also creates a sort of bubble around the entire solar system called the heliosphere, which blocks a lot of galactic cosmic radiation, Pevtsov said.

When activity is low, that bubble goes away, letting in galactic cosmic rays, which are a radioactive byproduct of supernova explosions. Those rays collide with Earth's outer atmosphere, causing it to shrink and change.

"That process also seems to seed more clouds, because they're very high energy particles, and they collide with the atmosphere and ionize it," Pevtsov said. "They penetrate very deep and create more clouds, and if there's increasing cloud cover, you'd have less solar penetration and that could cause some cooling."

Still, the effects are somewhat negligible when you compare the minor temperature changes that could come from increased cloud cover with those caused by greenhouse gases, he said.

And hopes that a low sunspot cycle could negate some of the impacts of global warming are probably far-fetched, he added.

"It won't have that much influence, but there is some effect from solar activity on the climate," Pevtsov said. "It's a lot less than the effect of greenhouse gasses."

But even though the big scary predictions of doom from the lack of sunspots aren't actually as big as they seem, or as scary, the period is still fascinating for scientists to study.

One thing they've learned more about during this low sunspot period is that for astronauts, exposure to galactic cosmic radiation is much worse than exposure to solar flares or other radiation in an active solar period.

"In the past they thought it was better to fly in periods with low sunspots," Pevtsov said. "But the high energy of cosmic rays is actually a lot harder to shield against. It's easier to shield astronauts from solar flares. So when you do a mission in space you want to fly during a high sunspot cycle, with low activity."

That's something that's hard to predict, but with the launch of some new solar satellites and probes in the next few years, predictions of active and inactive cycles could be a lot more accurate, he said.

Still, be careful what you wish for — if you're wishing for sunspot activity to increase again, Reeves said.

"Solar flares, coronal mass ejections and other things associated with increased activity can be a really bad thing for communications, navigation and satellites," Reeves said. "The National Academy of Science has been studying the societal consequences of an extremely large space weather event, if it disabled critical satellites."

That sort of activity could disable GPS systems, and disrupt broadcasts and cell phone connections, he said.

"Imagine if it disabled the ESPN satellite," Reeves added with a laugh. "Society would come to its knees."

And there have been some very minor indications that the cycle of increasing sunspots could start up again relatively soon, Pevtsov said.

"We've seen some extremely low activity that could indicate the cycle is changing," Pevtsov said. "And this minimum, it's not unique yet. We've seen cycles with much lower activity and less sunspots. But the longer it continues the more interesting it is. But that's no reason to panic, yet."

Contact Sue Vorenberg at svorenberg@sfnewmexican.com.