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Joined: 08 Nov 2001
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|Posted: Sat Apr 21, 2007 12:47 pm Post subject: 'Pipe organ' plays above the Sun
By Paul Rincon
Science reporter, BBC News, Preston
Immense coils of hot, electrified gas in the Sun's atmosphere behave like a musical instrument, scientists say.
These "coronal loops" carry acoustic waves in much the same way that sound is carried through a pipe organ.
(Coronal loops are generated
by the Sun's magnetic field)
Solar explosions called micro-flares generate sound booms which are then propagated along the coronal loops.
"The effect is much like plucking a guitar string," Professor Robert von Fay-Siebenbuergen told BBC News at the National Astronomy Meeting in Preston.
The corona is an atmosphere of hot, electrically-charged gas - or plasma - that surrounds the Sun. The temperature of the corona should drop the further one moves from the Sun.
But, in fact, the coronal temperature is up to 300 times hotter than the Sun's visible surface, or photosphere. And no one can explain why.
The coronal loops arch hundreds of thousands of kilometres above the Sun's surface like huge fiery fountains, and are generated by the Sun's magnetic field.
As solar plasma travels from the photosphere into the loops, it is heated from about 6,000 Kelvin (5,700C) to upwards of one million Kelvin.
Solar explosions called micro-flares can release energy equivalent to millions of hydrogen bombs.
These blasts can send immensely powerful acoustic waves hurtling through the loops at tens of kilometres per second, creating cosmic "organ music".
"These loops can be up to 100 million kilometres long and guide waves and oscillations in a similar way to a pipe organ," said Dr Youra Taroyan, from the Solar Physics and Space Plasma Research Centre (SP2RC) at the University of Sheffield.
The sound booms decay in less than an hour and dissipate in the very hot solar corona.
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