This is a scientific Americans 60 second science. I'm Jim David.

That strange sound? It's Earth's magnetosphere, the magnetic field created by the movement of the

iron core deep within the planet. The magnetosphere is a shield, protecting us from dangerous

cosmic rays, and it vibrates like a drum when jets of charged

particles from the sun called plasma crash into it. The theory describing

this phenomenon was developed in the 1970s but it wasn't until recently that we had the tools to observe it.

In 2007, NASA launched five satellites to study the magnetosphere in a mission called time history of events and macro scale

interactions during sub-storms or Themis. We ended up making use of all five NASA

Themis pros back very early in the mission actually when they were almost in a perfectly straight line

Martin Archer professor of physics and astronomy at Queen Mary University of London

and that that was really ideal for trying to tease apart

exactly what happens when something impulsive hits our magnetosphere. So basically what happened in this particular event is really

quite simple. You had a jet of plasma traveling very fast that impacted on the magnetopause, that's the boundary of our

magnetosphere. That then sent out ripples in all directions. Now some of those will then travel towards the north and southern poles and

get reflected back and it's the interference of the original and reflected waves

that allows these standing waves to form very much like the

surface of a drum and that gives it a very well defined frequency.

Archer's team converted the signals collected by the probes into all frequency. From the theory behind these drum-like oscillations, we know that they should have a big effect,

they should penetrate our magnetic shield quite far, causing motions within the regions where

there are the radiation belts for instance.

Certainly we saw perturbations on the ground in the magnetic field and that tells us that the ionosphere is moving as well

just in the same way as the boundary is so it's like one side of the

...