Saturn's Dusty Ionosphere

Michiko Morooka; Jan-Erik Wahlund; Lina Z. Hadid; Anders I. Eriksson; Niklas J. T. Edberg; Erik Vigren; David J. Andrews; A. M. Persoon; W. S. Kurth; D. A. Gurnett; W. M. Farrell; J. H. Waite; R. S. Perryman; M. Perry

doi:10.1029/2018JA026154

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Journal article

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Saturn's Dusty Ionosphere

Michiko Morooka, Jan-Erik Wahlund, Lina Z. Hadid, Anders I. Eriksson, Niklas J. T. Edberg, Erik Vigren, David J. Andrews, A. M. Persoon, W. S. Kurth, D. A. Gurnett, …

Journal of geophysical research. Space physics, Vol.124(3), pp.1679-1697

03/2019

DOI: 10.1029/2018JA026154

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Abstract

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.

dusty plasma

electron temperature

Fusion, Plasma and Space Physics

Fusion, plasma och rymdfysik

Fysik

Langmuir probe

Natural Sciences

Naturvetenskap

Physical Sciences

plasma density

Saturn's ionosphere

Details

Title: Subtitle: Saturn's Dusty Ionosphere
Creators: Michiko Morooka - Swedish Institute of Space Physics
Jan-Erik Wahlund - Swedish Institute of Space Physics
Lina Z. Hadid - Swedish Institute of Space Physics
Anders I. Eriksson - Swedish Institute of Space Physics
Niklas J. T. Edberg - Swedish Institute of Space Physics
Erik Vigren - Swedish Institute of Space Physics
David J. Andrews - Swedish Institute of Space Physics
A. M. Persoon - University of Iowa
W. S. Kurth - University of Iowa
D. A. Gurnett - University of Iowa
W. M. Farrell - Goddard Space Flight Center
J. H. Waite - Southwest Research Institute
R. S. Perryman - Southwest Research Institute
M. Perry - Johns Hopkins University Applied Physics Laboratory
Resource Type: Journal article
Publication Details: Journal of geophysical research. Space physics, Vol.124(3), pp.1679-1697
DOI: 10.1029/2018JA026154
ISSN: 2169-9402
eISSN: 2169-9402
Grant note: DOI: 10.13039/100006196, name: Jet Propulsion Laboratory, award: 1415150, 1405853, NNX13AG63G, NAS703001TONMO711123; DOI: 10.13039/501100001859, name: Swedish National Space Agency, award: Dnr 174/15, 135/13, 162/14; DOI: 10.13039/501100004359, name: Vetenskapsrådet, award: 621‐2013‐4191, 2.2.1‐312/16
Language: English
Date published: 03/2019
Academic Unit: Physics and Astronomy
Record Identifier: 9984455268402771

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