Do you know that our
planet Earth also sings (EarthSong)
which is tagged ‘Chorus’. In space,
it is believed that no one can hear you when you scream.
Nobody ever said anything
about singing, though. A NASA
(National Aeronautics Space Administration) spacecraft has beamed back a
beautiful song sung by our very own planet.
“It is called Chorus,
explains Craig Kletzing of the University of Iowa”. “This is one of the
clearest examples we’ve ever heard”. A ScienceCast video explores the
eerie-sounding radio emissions that come from our planet (watch video at: Sciencecast video).
Chorus is an
electromagnetic phenomenon caused by plasma waves in the Earth’s radiation
belts. For years, ham radio operators on Earth have been listening to this
sound from afar. Now, NASA’s twin ‘Radiation
Belt Storm Probes’ are travelling through the region of space where chorus
actually comes from – and the recording are out of this world.
“This is what the
radiation belt would sound like to a human being if we had radio antennas for
ears” says Kletzing, whose team at the University of Iowa built the ‘EMFISIS’ (Electronic and Magnetic Field
Instrument Suite and Integrated Science) receiver used to pick up the signals.
Chorus is not an acoustic
wave of the kind that travels through the air of our planet. Chorus is made of
radio waves that oscillate at acoustic frequencies between 0 and 10 kHz. The
magnetic search coil antennas of the Radiation Belt Storm Probes are designed
to detect these kinds of waves.
Chorus emissions are front
and centre for the Storm Probe Mission. They are thought to be one of the most
important waves for energizing electrons that make up the outer radiation belt.
In particular, Chorus might be responsible for the so-called ‘killer
electrons’, high-energy particles that cans endanger both satellites and
astronauts.
Many electrons in the
radiation belts are harmless, with too little energy to do damage to human or
electronic systems. But, sometimes, these electrons can catch a Chorus wave,
like a surfer riding a wave on Earth and gain enough energy to become dangerous
– or so researchers thinks.
