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ARE SUNSPOTS DISAPPEARING? by Dr Tony Phillips, Science@NASA Tucson, Arizona. But, he allows, "there is some evidence that they seranttl because sunspots are made of magnetism. The "firmament" of a sunspot is not matter but, rather, a strong magnetic field that appears dark because it blocks the upflow of heat from the Sun's interior. If Earth lost its magnetic field, the solid planet would remain intact; but if a sunspot loses its magnetism, it ceases to exist. "According to our measurements, sunspots seem to form only if the magnetic field is stronger than about 1500 gauss,” says Livingston. "If the current trend continues, we'l hit that threshold in the near future, and solar magnetic fields would become too weak to form sunspots.” “This work has caused a sensation in the field of solar physics,” comments NASA sunspot exper David Hathaway, who is not directly involved in the research. The controversy is not about the data. "We know Livingston and Penn are excellent observers,” says Hathaway. "The trend that they have discovered appears to be real." The part colleagues have trouble believing is the extrapolation. Hathaway notes that most of their data were taken after the maximum of Solar Cycle 23 (2000-2002) when sunspot activity naturally began to decline. "The drop in magnetic fields could be a normal aspect of the solar cycle and not a sign that sunspots are permanently vanishing." Penn himself wonders about these points. "Our technique is relatively new and the data stretches back in time only 17 years. We could be observing a temporary downturn that will reverse itself.” The technique they're using was pioneered by Livingston at the won't". he Sun is in the pits of the Tcepes solar minimum in nearly a century. Weeks and sometimes whole months go by without even a single tiny sunspot. The quiet has dragged out for more than two years, prompting some observers to wonder: are sunspots disappearing? "Personally, I'm betting that sunspots are coming back," says researcher Matt Penn of the National Solar Observatory (NSO) in Penn's colleague Bill Livingston of the NSO has been measuring the magnetic fields of sunspots for the past 17 years, and he has found a remarkable trend: sunspot magnetism is on the decline. "Sunspot magnetic fields are dropping by about 50 gauss per year,” says Penn. “If we extrapolate this trend into the future, sunspots could completely vanish around the year 2015." This disappearing act is possible Sunspot Magnetic Fields Data to Feb 2009 are 1995 2000 2005 2010 2015 Graph: Sunspot magnetic fields measured by Livingston and Penn from 1992 to February 2009 using an infrared Zeeman splitting technique. 46 * NEXUS OCTOBER - NOVEMBER 2009 www.nexusmagazine.com