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That Blinking Sun

The sun is covered in thousands of tiny hot spots, according to new observations from the Solar and Heliospheric Observatory (SOHO) satellite. These hot spots, as will be reported in Solar Physics, may shed light on two big questions facing solar science: the fantastically high temperatures of the sun's atmosphere and the source of the stream of charged particles called the solar wind.

When viewed in extreme ultraviolet light, the sun's surface looks dimpled, like an orange. The pattern results from the convection of hot gas, which wells up, cools, and sinks back below the surface. The intense heat rips apart atoms, creating charged particles that generate magnetic fields as they move. Solar physicist Richard Harrison, of the Rutherford Appleton Laboratory, near Oxford, U.K., was using a high-resolution spectrometer aboard SOHO to take a closer look at these constantly changing fields when he spotted something unusual.

All over the sun, relatively tiny spots--about the size of Earth--suddenly flare to temperatures of up to a million degrees Celsius, far above the average solar surface temperature of about 5500 degrees. The hot spots, dubbed blinkers, last just a few minutes before abruptly vanishing. Because the blinkers are concentrated at the fringes of the patches of convecting gases, Harrison believes that the magnetic field lines squeeze and heat the gas. "They seem to be occurring because these magnetic fields are getting rammed into one another," he says.

At any one moment about 3000 blinkers dot the sun's surface. "This work is very exciting because it can help us to understand the heating mechanism for the solar atmosphere, which is one of the mysteries which has plagued us for many years," says Helen Mason, of Cambridge University, U.K. It's not clear, though, whether the blinkers pack enough punch: "The energy we see at the moment is insufficient," Harrison admits. He argues, however, that visible blinkers might represent only a part of the total energy converted from tortured magnetic fields into heat.