Listen Closely And You’ll Hear Earth Sing

The twin Radiation Belt Storm probes launched in August 2012 will explore Earth’s Van Allen radiation belts for the next two years. The belts are regions of high-energy particles held in place by our planet’s magnetic field. Credit: NASA

Earth’s singin’ in a rain of electrons, and the twin the Radiation Belt Storm Probes (RBSP) are beaming back our planet’s eerie voice with astounding clarity. The vocals are created by waves of energized plasma sloshing around in the Van Allen radiation belts.

Called “chorus”, it sounds like chirps, whistles and dripping water. Give a listen HERE.

When most of us hear the word plasma, we think of the donating kind. The plasma the probes sample is a soup of ionized particles. Let me explain.

Stars are composed of an electrically conducting gas-like material called plasma.

Plasma makes up 99.9% of all the matter in the universe. Stars are made of plasma, the sun spews plasma from solar flares and a thin plasma permeates space. It resembles gas and is made of regular stuff like electrons (tiny particles whizzing around the nuclei of atoms), protons, hydrogen and iron atoms but with a difference – the particles aren’t neutral but carry an electric charge.

Unlike the familiar liquid, solid and gaseous forms of matter, plasmas have lost or gained an electron or two, often through intense heating, and conduct electricity. Under the influence of Earth’s magnetism (magnetic field) they flow hither and yon like twisty electric currents. “Wild stuff,” as Johnny Carson used to say.

If we could tune to the radio frequencies of speeding electrons in Earth’s magnetic field, we’d hear the odd chorus of plasma waves. Credit: NASA

Waves of plasma composed of electrons zinging around the Van Allen Belts emit very low frequency radio waves. The chirps are what our ears would hear if they could tune in to those waves. While the twin spacecraft have made excellent recordings of the plasma waves, ham radio operators and those using inexpensive Very Low Frequency (VLF) radios have been listening to them for years.

NASA plasma probes orbit in tandem through Earth’s radiation belts counting energetic particles, listening to plasma waves and sampling electromagnetic fields.  With two craft, scientist can map the 3D structure of the belts. Credit: NASA

Using a VLF receiver in a rural area away from powerlines, you’ll hear chorus when the northern lights are active. For more information on where to get a receiver and what to expect, check out my “How to Listen to the Aurora Borealis” blog.

The Van Allen Belts, named for their discoverer James Van Allen, are donut-shaped regions of high-energy electrons and protons surrounding the Earth. The lower belt begins at the top of the atmosphere and extends to 4,000 miles; the outer belt begins 8,000 miles up and reaches outward to 26,000 miles.  Most of the particles aren’t dangerous to spacecraft and astronauts but there are occasional “killer electrons” that ride waves of speeding plasma and do pose hazards.

The Van Allens are anything but static. Blasts of particles from the sun called coronal mass ejections (CMEs) can affect currents and particles within the belts. You’re probably already be familiar with CMEs, since they’re often responsible for sending waves of electrons and protons from the sun that spark the aurora borealis. The twin probes will map the structure and varying energy intensities within the belts as well as find out how normal electrons get amped up to become killers.

Like pondering the lyrics of the Beatles’ I am the Walrus, scientists will be looking for hidden meanings in the song of Earth.

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