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Jupiter sounds
Low radio frequencies are converted to sound wave frequencies
 real 28k

Monday, 18 December, 2000, 15:23 GMT
Listening to the 'sounds' of Jupiter
Jupiter Nasa
Jupiter and its moon Io as seen from approaching Cassini
By BBC News Online science editor Dr David Whitehouse

Ripples in magnetic fields wafting through interplanetary space have been detected by a space probe and converted into sound.

The "noises" were picked up the Cassini spacecraft which is en route to Saturn in 2004 via Jupiter.

The probe is detecting waves in the thin gas of charged particles that fills the space between the Sun and its planets.

The waves are in low radio frequencies and can be converted to sound wave frequencies to make the patterns audible.

Listening to the "sounds" of near-Jupiter space has been done before by the Pioneer and Voyager probes of the 1970's, but this is the first time that Cassini's data have been used in this way.

Oscillations

The waves were detected by Cassini's radio wave and plasma science instrument on 8 December, at a distance of about 23 million kilometres (14 million miles) from Jupiter.

Scientists believe that they arise from interactions between Jupiter's magnetic field and the solar wind of particles streaming away from the Sun.

Researchers point out that valuable information can be gleaned from this data. There are oscillations discernible that are produced by so-called ion-acoustic waves, the result of electrons pushed around by the energy in Jupiter's bow shock region.

The bow shock is similar to a sonic boom from a supersonic jet flying through Earth's atmosphere. Near Jupiter, the bow shock is caused by the superfast solar wind being diverted around Jupiter's magnetic field. The solar wind is heated, slowed and deflected.

Cassini has not yet reached Jupiter's bow-shock - this should occur in a few weeks from now. But the shock is probably the source of energy driving the waves that are reaching the spacecraft.

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See also:

09 Feb 00 | Sci/Tech
Jupiter's thunderous rising damp
19 May 00 | Sci/Tech
Io's wandering volcanoes
18 Aug 99 | Sci/Tech
Saturn probe swings by Earth
06 Oct 00 | Sci/Tech
Cassini approaches Jupiter
24 Oct 00 | Sci/Tech
Giant storms collide on Jupiter
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