olar scientists are getting an eyeful this summer-more than they had ever hoped for. Their sensitive solar instruments on board Skylab are clicking away in unison like finely tuned machines. (Such flawless performance is not guaranteed on any space mission let alone on a patched-up space station.) The resulting photographs of the sun have a clarity and resolution never before achieved. And that monstrous, churning, ever-changing ball of gas spewing out enough energy to feed a solar system (SN: 1/27/73, p. 61) is turning out to be much inore complex than they ever imagined. After only two months of looking through the telescopes' eyes at some 40,000 pictures of their favorite star, the scientists sit knee-deep in unanalyzed data, speak of mind-boggling phenomena and structure, and confess they don't know what it all means-yet. But the answers about how the sun works are all there just awaiting discovery, and they know it. The sun is full of mystery, the true teaser of science. The six telescopes in orbit photograph the sun simultaneously over a broad range of the electromagnetic spectrum (the first time this has been done). The photographs reveal features on the sun only hinted at before from rocket flights and ground based studies: features in the corona (the hot, thin outer atmosphere), the transition region, the chromosphere (the lower atmosphere) and the photosphere (the surface). The corona has yielded some of the biggest surprises. Before Skylab, most scientists studying the corona called it the quiet, homogeneous outer layer of the atmosphere. No more. "The quiet homogeneous corona doesn't exist anymore," says Giuseppe A. Vaiana of American Science and Engineering. Robert MacQueen of the High Altitude Observatory in Boulder agrees. "We see changes-dramatic, large-scale changes day by day and even orbit by orbit. We are impressed with the bewildering array of structure. The corona is a dynamic beast." The photographs reveal clearly for the first time the whole range of coronal features, from the intensely active regions to the weakest bright points, filament boundaries and the limb brightening in coronal holes. But the most impressive scenes in the corona are the ribbon-like structures that look like piles of spaghetti. These are the magnetic fields believed to trigger much of the sun's spectacular events. The fields themselves cannot be seen. But the plasma that follows the field lines can. These looped features, says Vaiana, emphasize .that the major force controlling and shaping the corona are the magnetic fields. The ribbons change with time, both in shape and in spectrum (what frequencies of light they emit). This was a surprise. "For decades we've been looking at the magnetic fields during flares and the fields never seemed to change," says Goetz Oertel, chief of solar science at NASA headquarters. Not only do the fields change, they sometimes change drastically. During a flare they may get unstable, blow up or combine. The larger ribbons become prominences that arch for hundreds of kilometers out in the corona. (See related story on Aug. 10 prominence, page 123.) On the other hand, during the June 15 flare (SN: 6/23/73, p. 402), the changes were not large-scale at all. "'The increase of surface brightness registered during the event [flare], from its moment of triggering to its peak, was in excess of a thousand," says Vaiana. But "the resulting structural changes in the region which flared are minimal in comparison with those shown previously. This indicates that N