A plasma wave instrument (PWI), also known as a plasma wave receiver, is a device capable of detecting vibrations in outer space plasma and transforming them into audible sound waves or air vibrations that can be heard by the human ear. This instrument was pioneered by then-

University of Iowa The University of Iowa (U of I, UIowa, or Iowa) is a public university, public research university in Iowa City, Iowa, United States. Founded in 1847, it is the oldest and largest university in the state. The University of Iowa is organized int ...

physics professor, Donald Gurnett. Plasma wave instruments are commonly employed on space probes such as GEOTAIL,

Polar Polar may refer to: Geography * Geographical pole, either of the two points on Earth where its axis of rotation intersects its surface ** Polar climate, the climate common in polar regions ** Polar regions of Earth, locations within the polar circ ...

Voyager Voyager may refer to: Computing and communications * LG Voyager, a mobile phone model manufactured by LG Electronics * NCR Voyager, a computer platform produced by NCR Corporation * Voyager (computer worm), a computer worm affecting Oracle ...

I and II (see

Plasma Wave Subsystem Plasma Wave Subsystem (sometimes called Plasma Wave System), abbreviated PWS, is an instrument that is on board the ''Voyager 1'' and ''Voyager 2'' unmanned probes of the Voyager program. The device is 16 channel step frequency receiver and a l ...

), and

Cassini–Huygens ''Cassini–Huygens'' ( ), commonly called ''Cassini'', was a space research, space-research mission by NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a space probe to study the planet Saturn and its system, i ...

Operating principle

Vibrations in the audible frequency range are perceived by humans when air vibrates against their

eardrum In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit changes in pres ...

. Air, or some other vibrating medium such as water, is essential for sound perception by the human ear. Without a medium to transmit it, the sound produced by a source will not be heard by a human. There is no air in outer space, nor is there any other type of medium capable of transmitting vibrations from a source to a human ear. However, there are sources in outer space that vibrate at frequencies audible to humans if only there were some transmitting medium to carry those vibrations from the source to a human eardrum. One such source capable of vibrating at audible frequencies (ranging from 45 to 20,000 vibrations per second) is plasma. Plasma is a collection of charged particles, such as free

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

s or

ionized Ionization or ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...

gas atoms. Examples of plasma include

solar flare A solar flare is a relatively intense, localized emission of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and ot ...

solar wind The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...

neon sign In the signage industry, neon signs are electric signs lighted by long luminous gas-discharge tubes that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in Decem ...

s, and

fluorescent lamp A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor ...

s. Plasma interacts with electrical and magnetic fields in ways that can result in vibrations across various frequencies, including the audible range.

Other applications

The recordings of interplanetary and outer space plasma vibrations, captured by plasma wave instruments, were provided by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

to composer

Terry Riley Terrence Mitchell Riley (born June 24, 1935) is an American composer and performing musician best known as a pioneer of the minimalist music, minimalist school of composition. Influenced by jazz and Indian classical music, his work became notab ...

and Kronos quartet founder David Harrington as inspiration for the composition of "''

Sun Rings ''Sun Rings'' is a Kronos Quartet project comprising pre-recorded sounds from space, images from space, music for string quartet and chorus composed by Terry Riley, and visuals by Willie Williams. It premiered 26 October 2002 at the Hancher Audit ...

''", a 85-minute multimedia piece for a

string quartet The term string quartet refers to either a type of musical composition or a group of four people who play them. Many composers from the mid-18th century onwards wrote string quartets. The associated musical ensemble consists of two Violin, violini ...

and choir. "''Sun Rings''" was performed November 3, 2006, at the Veteran's Auditorium, in

Providence, Rhode Island Providence () is the List of capitals in the United States, capital and List of municipalities in Rhode Island, most populous city of the U.S. state of Rhode Island. The county seat of Providence County, Rhode Island, Providence County, it is o ...

References

{{Reflist Plasma diagnostics Remote sensing Spacecraft instruments