Solved! Mystery of Missing Sunspots from 2008-2010

6a00d8341bf7f753ef0134876405a2970c.jpg Solar scientists from around the world were mystified when sunspots recently disappeared for more than two years, but a former Montana State University team solved the mystery and found a way to predict the next lapse in solar activity, which will help people who oversee communication systems or plan long trips into space, said MSU solar physicist Piet Martens.

Dibyendu Nandi, Andres Munoz-Jaramillo and Martens explained for the first time that the sunspots were missing from 2008 to 2010 because of a rare phenomenon, an extra-long "solar minimum," coincides with unusually weak magnetic fields at the sun's poles. The fields are ordinarily much stronger when solar activity is minimal.


Sunspots normally go through 11-year cycles. Sometimes sunspots are so abundant that they cover one percent of the sun's surface. Sometimes they disappear. But the recent lull lasted twice as long as usual, an unusual occurrence that last happened around 1913, Martens said. It happened at least once in the 19th century as well, in 1810. Understanding sunspots is important because solar activities influence space weather, which affects technology in space and on the Earth, Martens said.

Sunspots and solar flares shoot radiation and highly energetic particles toward Earth, which can interfere with airline travel, astronauts in space, sensitive equipment on satellites, short-wave communication and power grids, Martens explained. If scientists can predict space weather, people might minimize the damage by powering down satellites and diverting planes away from the North and South Poles, which are vulnerable to the extra radiation. Astronauts can hide behind lead shields.

Four days after a solar eruption takes place, its effects are felt on Earth, Martens said.

An extended lack of solar activity allows the accumulation of space junk, for example, because the normal rate of orbital decay slows down and almost stops. Space junk can include dead satellites orbiting the Earth.

A dearth of sunspots also makes space exploration more dangerous for humans – like those astronauts aboard the International Space Station — because planners are uncertain about exposure to galactic cosmic rays. Galactic cosmic rays intensify when solar activity dies down. In 2009 during the extended period without sunspots, cosmic ray intensities increased 19 percent beyond anything seen in the past 50 years.

"It's easier to shield against energetic protons from solar flares than from high-energy nuclei that make up galactic cosmic rays," Guhathakurta said. "Astronauts prefer solar maximum."

The Daily Galaxy via www.nasa.gov/sunearth

For a related MSU article, see "Sun goes longer than normal without producing sunspots" at http://www.montana.edu/cpa/news/nwview.php?article=5982

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