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Saturn's Dusty Ionosphere
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.ORCID iD: 0000-0001-9958-0241
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.ORCID iD: 0000-0002-2107-5859
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.ORCID iD: 0000-0003-2926-6761
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2019 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 3, p. 1679-1697Article in journal (Refereed) Published
Abstract [en]

Measurements of electrons and ions in Saturn's ionosphere down to 1,500-km altitudes as well as the ring crossing region above the ionosphere obtained by the Langmuir probe onboard the Cassini spacecraft are presented. Five nearly identical deep ionosphere flybys during the Grand Finale orbits and the Final plunge orbit revealed a rapid increase in the plasma densities and discrepancies between the electrons and ions densities (N-e and N-i) near the closest approach. The small N-e/N-i ratio indicates the presence of a dusty plasma, a plasma which charge carrier is dominated by negatively charged heavy particles. Comparison of the Langmuir probe obtained density with the light ion density obtained by the Ion and Neutral Mass Spectrometer confirmed the presence of heavy ions. An unexpected positive floating potential of the probe was also observed when N-e/N-i << 1. This suggests that Saturn's ionosphere near the density peak is in a dusty plasma state consisting of negatively and positively charged heavy cluster ions. The electron temperature (T-e) characteristics in the ionosphere are also investigated and unexpectedly high electron temperature value, up to 5000 K, has been observed below 2,500-km altitude in a region where electron-neutral collisions should be prominent. A well-defined relationship between T-e and N-e/N-i ratio was found, implying that the electron heating at low altitudes is related to the dusty plasma state of the ionosphere.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2019. Vol. 124, no 3, p. 1679-1697
Keywords [en]
Saturn's ionosphere, dusty plasma, Langmuir probe, plasma density, electron temperature
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:uu:diva-387566DOI: 10.1029/2018JA026154ISI: 000466087900016OAI: oai:DiVA.org:uu-387566DiVA, id: diva2:1329517
Funder
Swedish Research Council, 621-2013-4191Swedish Research Council, 2.2.1-312/16Swedish National Space Board, Dnr 174/15 135/13 162/14Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-06-24Bibliographically approved

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Morooka, MichikoWahlund, Jan-ErikHadid, Lina Z.Eriksson, Anders I.Edberg, Niklas J. T.Vigren, ErikAndrews, David J.

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Morooka, MichikoWahlund, Jan-ErikHadid, Lina Z.Eriksson, Anders I.Edberg, Niklas J. T.Vigren, ErikAndrews, David J.
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Swedish Institute of Space Physics, Uppsala Division
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Journal of Geophysical Research - Space Physics
Fusion, Plasma and Space Physics

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