Plasma waves travel between Saturn and Enceladus

Mission scientists converted Cassini recording of the plasma waves into a sound file.
By Laurel Kornfeld | Nov 24, 2018
Waves of plasma, ionized gas in which electrons wander freely among the nuclei of atoms, travel between Saturn, its moon Enceladus, and the giant planet's iconic rings.

Just two weeks before it was plunged into Saturn's atmosphere in September 2017, ending the mission, NASA's Cassini orbiter recorded the powerful interaction of plasma waves moving between the planet, its rings, and the moon. The recording revealed that the plasma waves travel on magnetic field lines that function like an electrical circuit, in which energy travels between several objects.

Described as the fourth state of matter after liquid, solid, and gas, plasma generates waves that carry energy, much the same way as air and water do. Cassini's Radio Plasma Wave Science (RPWS) instrument detected and recorded these waves in one of its close flybys of the giant planet.

"Enceladus is this little generator going around Saturn, and we know it is a continuous source of energy. Now we find that Saturn responds by launching signals in the form of plasma waves, through the circuit of magnetic field lines connecting it to Enceladus hundreds of thousands of miles away," noted RPWS team member Ali Sulaiman of the University of Iowa in Iowa City.

No such interaction occurs between the Earth and Moon. The dynamic activity between Saturn and Enceladus is caused by Enceladus being geologically active, as seen from its emission of water vapor plumes that become ionized in the environment around Saturn, and by its location within Saturn's powerful magnetic field.

Led by RPWS Principal Investigator Bill Kurth, the RPWS team at the University of Iowa converted Cassini's recording of the plasma waves in the audio frequency range into an audio file in a manner similar to that used by radio waves to turn electromagnetic waves into music.Compressed from 16 minutes to 28.5 seconds, the audio file is characterized by a "whooshing" sound.

Two papers detailing the findings have been published here and here in the journal Geophysical Research Letters.

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