Sun's Lull Linked to Altered Plasma Conveyor Belt
A graph from 2006 predicting the intensity of the current (23) and next (24) solar cycles, based on a computer model.
Credit: NASA

A long lull in solar activity recently may have been caused by changes in the conveyor-belt-like process that moves material around the surface of our star, a new study found.

The conveyor belt pushed plasma farther out toward the sun's poles, and in a slower flow, than it normally does, new computer models suggest. These variations may have helped to extend an unusually long period of solar calm recently, the findings suggest.

Solar El Ni?o

The sun goes through cycles lasting approximately 11 years that include phases with increased magnetic activity, more sunspots, and more solar flares, and phases with less activity. Puzzlingly, solar cycle 23, which ended recently, lasted longer than previous cycles, with a prolonged phase of low activity that scientists had difficulty explaining.

Variations in solar weather modeled in the new study are akin to El Ni?o-like climate patterns on Earth.

Just as Earth's global ocean circulation transports water and heat around the planet and regulates the El Ni?o effect, the sun has a conveyor belt in which plasma flows along the surface toward the poles and then returns toward the equator, transporting magnetic flux along the way.

Recent measurements show that in solar cycle 23, the flow of plasma along the sun's surface extended all the way to the poles, while in previous solar cycles the flow turned back toward the equator at about 60 degrees latitude.

Furthermore, the return flow was slower in cycle 23 than in previous cycles.

This longer timescale and varied reach of the sun's conveyor belt effect could have caused the longer duration of cycle 23, the new model suggests.

Affecting Earth

Understanding solar weather is important because outbursts of charged particles from the sun can greatly affect life on Earth, hindering electronics on satellites and disrupting power grids on the ground.

The new findings come on the heels of the sun's latest eruption, called a coronal mass ejection, which blasted a stream of ionized gas heading straight for Earth.

The solar eruption, which occurred Sunday, reached our planet Tuesday, leading to an increase in aurora activity that was visible to skywatchers in Alaska, Canada and the northern U.S. mainland. The stunning northern lights show continued to Wednesday.

The results should help scientists better understand the factors controlling the timing of the solar cycles and could lead to better predictions, the researchers said.