Thursday, September 27, 2012
Sounds of Space: "Chorus" radio waves within Earth's magnetosphere
This is the Earth's song, pinging out contended chirrups into deep space.
The haunting sounds have been captured by Nasa's twin Radiation Belt Storm Probe (RBSP) satellite, which launched on August 30 this year.
The satellites captured the chirping and whistling radio waves emitted by Earth’s magnetosphere on September 5.
The sound is known as 'Earth's chorus' and can be heard by human ears - that is, assuming you could take your helmet off while floating in space.
Craig Kletzing, from the University of Iowa, is the principal investigator of the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instruments on-board the satellites.
The sounds of Earth: As charged solar particles hit the inner and outer radiation belts around our planet, they get caught and whipped around, emitting the sounds which you can hear below
He said: 'People have known about chorus for decades.
'Radio receivers are used to pick it up, and it sounds a lot like birds chirping.
'It was often more easily picked up in the mornings, which along with the chirping sound is why it’s sometimes referred to as "dawn chorus".'
The radio waves are at frequencies which can be heard from the human ear, but sadly you might need to be in space and without a helmet - which is not medically advisable.
You might also encounter the tricky problem of sound not travelling through the vacuum.
The sounds are emitted by energetic particles in the upper levels of Earth’s magnetosphere, before they get whipped around by the radiation belts circling the Earth.
The satellites trail each other around the Earth in elliptical orbits - sometimes as low as 375 miles about the ground, other times up to 20,000 miles above us.
They are aiming to study the Van Allen belts that circle the Earth, in particular the various particles that make up the radiation belts.
The Van Allen belts are streams of particles, which arrive in Earth's vicinity from the solar winds and get caught in Earth's magnetic field.
Nicky Fox, the deputy project scientist at Johns Hopkins University Applied Physics Laboratory, said:'If you imagine having two buoys in the ocean, and one goes up, and comes down again, you don't know anything about what caused that to go up and down,
'If both of them go up, then you know you've got a very big feature that is affecting both of them at the same time. If you one goes up, then the other goes up, you can measure how fast that wave has traveled between them, and what direction it's going into.
'And if only one goes up and comes down again, then you've got a very, very localised feature that didn't travel anywhere.
'So in order to be able to really understand what is going on, these very fine-scale features in our radiation belts, we have two spacecraft to do that.'
There is poetic justice - or more likely intent - in Kletzing heading up the research at the University of Iowa - as that is where James Van Allen first studied the belts in the 1950s.