A swirl on the sun's blotchy face.

A swirl on the sun's blotchy face

The Earth has its hurricanes and tornadoes; Jupiter has its Great Red Spot and other swirling features. Now solar scientists report detecting a strong whirlpool in an otherwise quiet region of the sun's atmosphere. About 5,000 kilometers across, this recently observed solar vortex would be large enough to swallow up much of the Earth yet represents only a tiny fraction of the sun's 1.4-million-kilometer diameter.

"We believe this is the first report of a stable vortex structure in the turbulent convection of the solar atmosphere," say researchers from the Lockheed Palo Alto (Calif.) Research Laboratory and their colleagues in Sweden and West Germany. The group reports its findings in the Sept. 15 NATURE.

The researchers found the vortex by observing the motion of solar granules, light-colored patches that give the sun a blotchy appearance. These granules, each one typically 1,000 kilometers across, indicate the presence of hotter fluid forced up by convection near the sun's surface. Behaving somewhat like corks bobbing in a stream, the granules--as they appear, move and disappear -- mark the vortex's position.

Normally, the Earth's atmosphere blurs the details of such granule motions, as seen by Earth-based observers. However, the combination of extraordinarily clear skies above the new Swedish Solar Observatory in the Canary Islands and sophisticated image-processing technology allowed the researchers to track the motion of a cluster of granules in one portion of the solar atmosphere. Although individual granules appeared and disappeared on the scale of minutes, the vortex itself persisted for at least 1.5 hours, the length of time over which the granules were observed.

Further investigations are needed to determine how often such vortices appear and how long they last, the scientists say. Their observation of a vortex within a small field of view already suggests that vortices are likely to occur frequently.

Convection of hot gases in the sun's atmosphere plays an important role in distorting and shifting the sun's magnetic field. In principle, swirling motions can twist magnetic fields and induce electric currents that can heat up solar gases. If such vortices turn out to be a common feature of the sun's convection zone, they may provide an important mechanism for heating the outer atmosphere, or corona, to high temperatures.