March 6, 2006<br /><br />Dwayne Brown/Erica Hupp <br />Headquarters, Washington <br />(202) 358-1726/1237 <br /><br />Bill Steigerwald/Nancy Neal-Jones <br />Goddard Space Flight Center, Greenbelt, Md. <br />(301) 286-5017/0039 <br /><br />RELEASE: 06-087<br /><br />NASA AIDS IN RESOLVING LONG STANDING SOLAR CYCLE MYSTERY<br /><br />Scientists predict the next solar activity cycle will be 30 to 50 <br />percent stronger than the previous one and up to a year late. <br />Accurately predicting the sun's cycles will help plan for the effects <br />of solar storms. The storms can disrupt satellite orbits and <br />electronics; interfere with radio communication; damage power <br />systems; and can be hazardous to unprotected astronauts. <br /><br />The breakthrough "solar climate" forecast by Mausumi Dikpati and <br />colleagues at the National Center for Atmospheric Research in <br />Boulder, Colo. was made with a combination of computer simulation and <br />groundbreaking observations of the solar interior from space using <br />NASA's Solar and Heliospheric Observatory (SOHO). NASA's Living With <br />a Star program and the National Science Foundation funded the <br />research. <br /><br />The sun goes through a roughly 11-year cycle of activity, from stormy <br />to quiet and back again. Solar storms begin with tangled magnetic <br />fields generated by the sun's churning electrically charged gas <br />(plasma). Like a rubber band twisted too far, solar magnetic fields <br />can suddenly snap to a new shape, releasing tremendous energy as a <br />flare or a coronal mass ejection (CME). This violent solar activity <br />often occurs near sunspots, dark regions on the sun caused by <br />concentrated magnetic fields. <br /><br />Understanding plasma flows in the sun's interior is essential to <br />predicting the solar activity cycle. Plasma currents within the sun <br />transport, concentrate, and help dissipate solar magnetic fields. "We <br />understood these flows in a general way, but the details were <br />unclear, so we could not use them to make predictions before," <br />Dikpati said. Her paper about this research was published in the <br />March 3 online edition of Geophysical Research Letters. <br /><br />The new technique of "helioseismology" revealed these details by <br />allowing researchers to see inside the sun. Helioseismology traces <br />sound waves reverberating inside the sun to build up a picture of the <br />interior, similar to the way an ultrasound scan is used to create a <br />picture of an unborn baby. <br /><br />Two major plasma flows govern the cycle. The first acts like a <br />conveyor belt. Deep beneath the surface, plasma flows from the poles <br />to the equator. At the equator, the plasma rises and flows back to <br />the poles, where it sinks and repeats. The second flow acts like a <br />taffy pull. The surface layer of the sun rotates faster at the <br />equator than it does near the poles. Since the large-scale solar <br />magnetic field crosses the equator as it goes from pole to pole, it <br />gets wrapped around the equator, over and over again, by the faster <br />rotation there. This is what periodically concentrates the solar <br />magnetic field, leading to peaks in solar storm activity. <br /><br />"Precise helioseismic observations of the 'conveyor belt' flow speed <br />by the Michelson Doppler Imager (MDI) instrument on board SOHO gave <br />us a breakthrough," Dikpati said. "We now know it takes two cycles to <br />fill half the belt with magnetic field and another two cycles to fill <br />the other half. Because of this, the next solar cycle depends on <br />characteristics from as far back as 40 years previously - the sun has <br />a magnetic 'memory'." <br /><br />The magnetic data input comes from the SOHO/MDI instrument and <br />historical records. Computer analysis of the past eight years' <br />magnetic data matched actual observations over the last 80 years. The <br />team added magnetic data and ran the model ahead 10 years to get <br />their prediction for the next cycle. The sun is in the quiet period <br />for the current cycle (cycle 23). <br /><br />The team predicts the next cycle will begin with an increase in solar <br />activity in late 2007 or early 2008, and there will be 30 to 50 <br />percent more sunspots, flares, and CMEs in cycle 24. This is about <br />one year later than the prediction using previous methods, which rely <br />on such statistics as the strength of the large-scale solar magnetic <br />field and the number of sunspots to make estimates for the next <br />cycle. This work will be advanced by more detail observations from <br />the Solar Dynamics Observatory, scheduled to launch in August 2008. <br /><br />SOHO is a project of international collaboration between NASA and the <br />European Space Agency. For images explaining the data on the Web, <br />visit: <br /><br />http://www.nasa.gov/vision/universe/solarsystem/solar_cycle_graphics.html <br /><br /><br />For information about NASA and agency programs on the Web, visit: <br /><br />http://www.nasa.gov/home