Scientists using a new computer model at the National Center for Atmospheric Research said they now understand what drives the Sun's 11-year cycle of sunspot activity, and they are confident the model can help them predict the cycle accurately enough to allow NASA and the satellite and electric-power industries prepare for periods of maximum solar magnetic activity years in advance.

The peak of the cycle, called the Solar Maximum, generates more frequent magnetic storms and ejections of energetic particles that can slow satellite orbits - thereby interfering with global navigation � as well as disrupt communications and bring down power systems.

During a telephone briefing for reporters Monday, the scientists said they have great confidence in the forecast, because their model has matched the historical data from the past eight solar cycles with more than 98 percent accuracy.

"Our model has demonstrated the necessary skill to be used as a forecasting tool," said NCAR scientist Mausumi Dikpati, the research team leader at NCAR's High Altitude Observatory.

Their Predictive Flux-transport Dynamo Model is enabling NCAR scientists to predict that the next solar cycle, known as Cycle 24, will produce sunspots across an area slightly larger than 2.5 percent of the visible surface of the Sun. They said they expect the cycle to begin in late 2007 or early 2008, which is about six months to 12 months later than a cycle would normally start. Cycle 24 is expected to reach its peak sometime in 2012.

"We disagree with the timing," said David Hathaway, a solar astronomer at NASA's Marshall Space Flight Center in Huntsville, Ala. "The large (solar) cycles tend to start early. We think the cycle will start this year."

Hathaway explained that his group also foresees a large and long solar cycle coming next, but "when we look at the statistics, for us the statistics are stronger for a big cycle starting early" � although he admitted that the data remain unclear. "It hasn't been well-measured," he told reporters.

Both groups said the model should help them to forecast sunspot activity for two solar cycles, or 22 years, into the future. The NCAR team is planning in the next year to issue a forecast of Cycle 25, which will peak in the early 2020s.

"This is a significant breakthrough with important applications especially for satellite-dependent sectors of society," said Peter Gilman, an NCAR scientist.

The team generated its forecast, in part, by tracking sub-surface movements of the sunspot remnants of the previous two solar cycles.

The Sun goes through approximately cycles from peak storm activity to quiet and back again. Solar scientists have been tracking the cycles since 1880, but without being able to predict relative intensity or timing. The storms are linked to twisted magnetic fields in the Sun that suddenly snap and release tremendous amounts of energy � Hathaway said the fields "short-circuit" the process.

The storms tend to occur near dark regions of concentrated magnetic fields, popularly known as sunspots.

The NCAR team's computer model draws on research indicating the evolution of sunspots is caused by a current of plasma, or electrified gas, which circulates between the solar equator and its poles over a period of 17 to 22 years. This current acts like a conveyor belt of sunspots.

As explained by Madhulika Guhathakurta, lead scientist with NASA's Living With a Star program in Washington, D.C., the sunspot process begins with tightly concentrated magnetic field lines in the solar convection zone - the outermost layer of the Sun's interior.

The field lines rise to the surface at latitudes near the equator and form bipolar sunspots, regions of concentrated magnetic fields. When these sunspots decay, they imprint the moving plasma with a type of magnetic signature.

As the plasma travels toward the poles, it sinks about 200,000 kilometers (124,000 miles) back into the convection zone and starts returning toward the equator at a speed of about one meter (three feet) per second or slower. The increasingly concentrated fields become stretched and twisted by the internal rotation of the Sun as they near the equator, gradually becoming less stable than the surrounding plasma.

This eventually causes coiled-up magnetic field lines to rise up, tear through the Sun's surface, and create new sunspots.

The subsurface plasma flow used in the model has been verified with the relatively new technique called helioseismology, based on observations from both NSF� and NASA�supported instruments, such as the SOHO spacecraft and several terrestrial telescopes � including Kitt Peak in Arizona and Mount Wilson and Sacramento Peak in California.

This technique tracks sound waves reverberating inside the Sun to reveal details about the interior, much as a doctor might use an ultrasound to see inside a patient.

The team is publishing its forecast in the current issue of Geophysical Research Letters.

Related Links
NCAR

Memory Foam Mattress Review

SPACE MEDIA NETWORK PROMOTIONS Solar Energy Solutions Tempur-Pedic Mattress Comparison ... Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News