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Alternating currents cause the aurora of Jupiter



Jupiter

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An international team of researchers has managed to measure the current system responsible for the aurora of Jupiter. Using data transmitted to Earth by NASA's Juno spacecraft, they showed that direct currents were much weaker than expected and that alternate currents must play a special role. On Earth, on the other hand, a DC system creates its aurora. The Jupiter electric current system is maintained in particular thanks to the large centrifugal forces, which release ionized sulfur dioxide gas from the moon Io of the gaseous giant through the magnetosphere.

Professor Dr. Joachim Saur, of the Institute of Geophysics and Meteorology of the University of Cologne, participated in the project. The article "Birkeland currents in the Jupiter magnetosphere observed by the Juno spacecraft in polar orbit" is published in the current issue of Nature astronomy.

Jupiter, the largest planet in the solar system, has the brightest aurora, with a radiant power of 100 terawatts (100,000,000,000 kilowatts = one hundred billion kW). It would take 100,000 power plants to produce this light. As on Earth, the aurora of Jupiter shows itself as two huge oval rings around the poles. They are driven by a gigantic system of electric currents that connect the region of polar light with the magnetosphere of Jupiter. The magnetosphere is the region around a planet that is influenced by its magnetic field. Most electric currents run along the lines of Jupiter's magnetic field, also known as Birkeland currents.

NASA's Juno spacecraft has been in a polar orbit around Jupiter since July 2016. Its goal is to better understand the interior and the aurora of Jupiter. Juno has now measured for the first time the electric direct current system responsible for the aurora of Jupiter. For this purpose, the scientists measured the magnetic field environment of Jupiter with high precision to derive electrical currents. The total current is approximately 50 million amperes. However, this value is clearly below the theoretically expected values. The reason for this deviation are small-scale turbulent alternating currents (also known as alfundicas currents), which have so far received little attention. "These observations, combined with other Juno spacecraft measurements, show that alternating currents play a much greater role in the generation of Jupiter's aurora than the DC system," said Joachim Saur. He has been investigating these turbulent alternate currents for 15 years, highlighting their importance. The aurora of Jupiter differs from those of the Earth, which are essentially generated by direct currents. The northern lights of the Earth shine a thousand times fainter because the Earth is smaller than Jupiter, has a weaker magnetic field and rotates more slowly.

"Jupiter's electric current systems are driven by the enormous centrifugal forces in Jupiter's fast-rotating magnetosphere," said Saur. Jupiter's moon Io, volcanically active, produces one ton of sulfur dioxide gas per second, which is ionized in Jupiter's magnetosphere. "Due to the rapid rotation of Jupiter, a day in Jupiter lasts only ten hours, the centrifugal forces move the ionized gas in the magnetic field of Jupiter, which generates the electric currents," the geophysicist concludes.


Juno finds changes in the magnetic field of Jupiter.


More information:
Stavros Kotsiaros and others, Birkeland currents in the Jupiter magnetosphere observed by the polar-orbiting Juno spacecraft, Nature astronomy (2019). DOI: 10.1038 / s41550-019-0819-7

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The alternate currents cause the aurora of Jupiter (2019, July 11)
recovered on July 12, 2019
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