Solar scientists from around the world were puzzled when sunspots disappeared for more than two years, but a team of scientists from Montana State University has solved the mystery and found a way to predict the next lapse in solar activity.
Three MSU scientists -- Dibyendu Nandi, Andres Munoz-Jaramillo and Piet Martens -- published a paper in the March 3 issue of Nature explaining for the first time why sunspots were missing from 2008 to 2010.
Sunspots normally have 11-year cycles. Sometimes sunspots are so abundant that they cover 1 percent of the sun's surface. Sometimes they disappear. But the recent lull lasted twice as long as usual.
The last time such a thing occurred was around 1913, Martens said. Before that, it happened in 1810.
The discovery that the rare phenomenon, an extra-long "solar minimum," coincides with unusually weak magnetic fields at the sun's poles has drawn widespread attention, with NASA scheduling a teleconference to discuss it and journalists from around the world contacting team members for interviews.
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, he said.
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 and putting astronauts behind lead shields.
Martens said solar physicists everywhere noticed that the sun was quiet for an unusually long time during the last sunspot cycle. They wondered how long it would last and tried to model the phenomenon on their computers.
The three MSU scientists succeeded because of two things: Munoz-Jaramillo's work on a computer program that made it possible to model emerging sunspots in new ways; and Nandi's idea to use Munoz-Jaramillo's program to study the lack of sunspots.
Those things led the scientists to simulate 210 sunspot cycles and discover the relationship between extended spotless periods and weak magnetic fields at the solar poles.
They identified that variations in a hot plasma flow in the sun's interior, known as the meridional circulation, is the likely reason behind the lack of sunspots and a weak magnetic field at the sun's poles.
Martens and MSU associate research professor David McKenzie helped design and calibrate four telescopes that were launched on the Solar Dynamics Observatory satellite, the first mission in NASA's Living with a Star program and the most advanced spacecraft ever designed to study the sun.
Martens said he hopes he, Nandi and Munoz-Jaramillo - natives of three different countries -- will continue to collaborate, although Nandi has returned to his native India where he is an assistant professor at the new Indian Institute of Science Education and Research in Kolkata and Munoz-Jaramillo, a native of Colombia, is a visiting fellow at the Harvard-Smithsonian Center for Astrophysics.