The sun has been surprisingly quiet lately, and until now astronomers couldn't figure out why. An 11-year cycle governs solar flares and sunspots, and researchers knew that we were at the end of a cycle in a "solar minimum" or quiet period--but that somnolence has continued for an extra year beyond the point at which researchers expected sunspot activity to resume. Comments Australian astronomer Phil Wilkinson:
"We have had a drought of sunspots.... This is the longest period the sun has been quiet since the start of the Space Age. Seeing the sun doing nothing is really exciting," he said, adding it made physicists wonder how little they really understood [Sydney Morning Herald].
Now, new observations announced at a meeting of the American Astronomical Society reveal a possible explanation: "sluggish" solar jet streams 4,350 miles below the surface of the sun.
Every 11 years, the sun simultaneously generates twin streams of plasma at each of its poles. Unlike the jet streams on Earth, the solar versions are magnetized and travel only toward the equator. This migration takes place very slowly--at about 10 kilometers per hour. For reasons still not understood, when the streams reach 22 degrees of latitude, north and south, they touch off a new solar cycle, and the sunspots reappear [ScienceNOW Daily News].
National Solar Observatory researchers Frank Hill and Rachel Howe monitored the jet stream with ground- and space-based telescopes, using
a relatively new science called helioseismology that traces sound waves to reveal conditions in the Sun’s interior [Physics World].
They studied subtle movements in the Sun’s outer layer to trace the movement of the buried jet stream, and determined that the stream had taken an extra year to migrate down towards the equator--although it is now reaching the critical latitude point.
"The sunspot cycle is about to take off," [Hill] adds, based on the latest solar jet stream measurements [USA Today].
As for why the jet stream was moving slower than usual--well, researchers don't have an answer for that yet. But there are a lot of things that researchers don't yet understand about the sun's behavior. To try to answer some questions, another group of researchers has also created the first ever model of an entire sunspot (pictured), using a supercomputer to calculate its dynamics, crunching data from 1.8 billion individual points. The model, described in a paper in Science, may help explain both earthly and solar phenomenon. Says lead researcher Matthias Rempel:
"If you want to understand all the drivers of Earth's atmospheric system, you have to understand how sunspots emerge and evolve." ... Solar flares and coronal mass ejections are typically found in magnetically active regions around groupings of sunspots. These plasma storms can buffet the Earth's atmosphere and disrupt power grids, satellites and other systems [Live Science].
Related Content: Bad Astronomy: Here comes the Sun(spot)! has more on the recent sunspot findings 80beats: New Images Herald an Improved Solar-Storm Early Warning System DISCOVER: Space Weather and the havoc it can cause DISCOVER: Seeing Sun Storms in Stereo Image: UCAR / Matthias Rempel, NCAR
