'Pipe organ' plays above the Sun
Coronal loops are generated by the Sun's magnetic field Acoustic
waves 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. 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.
Nuclear fusion is the same process which powers the Sun and other
stars. Unlike the burning of fossil fuels, fusion reactions produce no
carbon dioxide, the greenhouse gas blamed by scientists for warming the
planet.
BBC NEWS
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