Craft eyes solar storms, hints at cooler core.

An orbiting observatory has spied a dozen tornadoes in the sun's atmosphere, each nearly as wide as Earth and swirling faster than 50,000 kilometers per hour. Other data from the spacecraft, known as SOHO (Solar and Heliospheric Observatory), hint that the sun's fiery core is either misshapen or slightly cooler than expected.

The tornadoes lie at the sun's poles--the same regions where darker, cooler parts of the atmosphere, known as coronal holes, are concentrated. From these holes emanates the fastest component of the stream of charged particles called the solar wind.

"We now need to see if the characteristics of the tornado events make them likely to be significant contributors to the origin of the wind," says C. David Pike of the Rutherford Appleton Laboratory in Chilton, England. He and Helen E. Mason of the University of Cambridge in England presented the findings this week at a press briefing at Rutherford. They also describe their work in an upcoming Solar Physics.

Pike and Mason deduced the presence of tornadoes from measurements taken by SOHO's coronal diagnostic spectrometer. The researchers found that the ultraviolet radiation emitted by ionized oxygen atoms was shifted to both longer and shorter wavelengths, as if some of the material were moving toward Earth and some away from it. That pattern is characteristic of a tornadolike swirl of gas.

It's not surprising that the turbulent sun, whose motions twist magnetic fields and unleash enormous amounts of energy, would possess stormlike features, says Douglas Gough of Cambridge. Astronomers have previously discovered such motion at the sun's lower depths, notes Pike.

Less definitive, more puzzling data from other SOHO instruments suggest that the sun's hydrogen-burning core is something of a wimp. From measurements of the rise and fall of the solar surface, Gough and his colleagues deduce that sound waves at the core are traveling slightly less rapidly--about 0.1 percent less--than the standard model indicates. This suggests a lower temperature at the core, because sound waves slow down as a medium becomes cooler.

Alternatively, the core may be misshapen. If it resembles a football or a lemon instead of a perfect sphere, sound waves would travel more slowly.

Even if the core is generating less heat than predicted, its performance could be temporary, Gough notes. Complicating matters, theorists may not have an accurate fix on the rate at which the core consumes hydrogen to generate heat. "My hope is that when we've accumulated more data from SOHO, we will be able to determine" the true nature of the core, Gough says.

NASA and the European Space Agency recently announced that they will fund SOHO through 2003. That will enable the craft to view the sun at its most temperamental, during the peak of its sunspot cycle, expected in 2000.