SCI-TECH & AGRI

Hypervelocity winds rage in the sun

WINDS OF electrified gas rip through the solar atmosphere at nearly the speed of sound there, according to new observations from NASA's Transition Region and Coronal Explorer (TRACE) spacecraft

The new resultshows that the winds and storms of the solar atmosphere at speeds up to 200,000 miles per hour (about 320,000 kilometers/hour) are so intense that they are more important than gravity in determining the density of the atmosphere.

"This discovery completely changes our understanding of coronal loops, immense, arch-shaped structures of electrified gas that comprise the Sun's outer atmosphere (corona)," said Amy Winebarger, in Astrophysical Journal.

The solar atmosphere is permeated with magnetic fields, generated by electrified gas, or plasma, churning violently beneath the visible surface.

Solar astronomers have long observed loops of plasma, called coronal loops, which appear to trace out the corona's complex magnetic-field structure. Coronal loops come in various sizes, but most are enormous, capable of spanning several Earths.

The strong pull of solar gravity led astronomers to believe that the plasma should be dense at the bases of the loop and thin at the top, just as the Earth's gravity pulls our atmosphere close to the surface, causing it to thin with increasing altitude.

In fact, coronal loops seem to be about the same density throughout their height, even though some of them extend several hundred thousand miles (over a million kilometres) above the solar surface.

If coronal loops are indeed currents of plasma being propelled against solar gravity, they would have about the same density along their entire height, just like the arc of water from a water fountain.

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