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Wahlund JE, Morooka MW, Hadid LZ, Persoon AM, Farrell WM, Gurnett DA, Hospodarsky G, Kurth WS, Ye SY, Andrews DJ, Edberg NJT, Eriksson AI, Vigren E. In situ measurements of Saturn's ionosphere show that it is dynamic and interacts with the rings. Science 2017; 359:66-68. [PMID: 29229651 DOI: 10.1126/science.aao4134] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 11/27/2017] [Indexed: 11/02/2022]
Abstract
The ionized upper layer of Saturn's atmosphere, its ionosphere, provides a closure of currents mediated by the magnetic field to other electrically charged regions (for example, rings) and hosts ion-molecule chemistry. In 2017, the Cassini spacecraft passed inside the planet's rings, allowing in situ measurements of the ionosphere. The Radio and Plasma Wave Science instrument detected a cold, dense, and dynamic ionosphere at Saturn that interacts with the rings. Plasma densities reached up to 1000 cubic centimeters, and electron temperatures were below 1160 kelvin near closest approach. The density varied between orbits by up to two orders of magnitude. Saturn's A- and B-rings cast a shadow on the planet that reduced ionization in the upper atmosphere, causing a north-south asymmetry.
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Affiliation(s)
- J-E Wahlund
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden.
| | - M W Morooka
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
| | - L Z Hadid
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
| | - A M Persoon
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA
| | - W M Farrell
- Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - D A Gurnett
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA
| | - G Hospodarsky
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA
| | - W S Kurth
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA
| | - S-Y Ye
- Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA
| | - D J Andrews
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
| | - N J T Edberg
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
| | - A I Eriksson
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
| | - E Vigren
- Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala, Sweden
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