Auroral kilometric radiation (AKR) is the intense radio radiation emitted in the acceleration zone (at a height of three times the radius of the Earth) of the polar lights. The radiation mainly comes from

cyclotron radiation Cyclotron radiation is electromagnetic radiation emitted by non-relativistic accelerating charged particles deflected by a magnetic field. The Lorentz force on the particles acts perpendicular to both the magnetic field lines and the particles' mot ...

from

electrons The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...

orbiting around the magnetic field lines of the Earth. The radiation has a

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

of between 50 and 500 kHz and a total

power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may a ...

of between about 1 million and 10 million

watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...

s. The radiation is absorbed by the ionosphere and therefore can only be measured by satellites positioned at vast heights, such as the Fast Auroral Snapshot Explorer (FAST). According to the data of the

Cluster mission Cluster II is a space mission of the European Space Agency, with NASA participation, to study the Earth's magnetosphere over the course of nearly two solar cycles. The mission is composed of four identical spacecraft flying in a tetrahedral form ...

, it is beamed out in the cosmos in a narrow plane tangent to the magnetic field at the source. The sound produced by playing AKR over an audio device has been described as "whistles", "chirps", and even "screams". As some other planets emit cyclotron radiation too, AKR could be used to learn more about

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...

, Saturn,

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...

and Neptune, and to detect

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

References

* Radio astronomy Planetary science {{astronomy-stub