HELSINKI, Finland, Sept. 28 (UPI) -- The astronomical phenomenon of the Northern Lights has become more rare in recent years than at any time in more than a century, scientists say.
The Northern Lights, or aurora borealis, generally follow an 11-year "solar cycle" in which the frequency of the phenomena rises to a maximum, tapers off into a minimum and then repeats the cycle, the BBC reports.
But researchers at the Finnish Meteorological Institute say the minimum point, officially reached in 2008, is "going on and on and on."
"Only in the past half a year have we seen more activity, but we don't really know whether we're coming out of this minimum," researchers Noora Partamies said.
The Northern Lights are triggered by solar winds hitting Earth and being drawn to the magnetic poles, energizing electrons in the parts of the atmosphere known as the ionosphere and magnetosphere.
A lessening of the Northern Lights is a signal that activities on the sun that cause solar winds, such as solar flares and sun sports, are also quieting down.
This is the first time researchers have been able to use a network of modern observation stations to track a solar cycle when it becomes as severely disrupted as it seems now.
"We're waiting to see what happens, is the next maximum going to be on time, is it going to be late, is it going to be huge?" Partamies said.