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AGU: Geophysical Research Letters

 

Index Terms

  • Planetary Sciences: Fluid Planets: Interactions with particles and fields
  • Planetary Sciences: Fluid Planets: Magnetospheres
  • Planetary Sciences: Fluid Planets: Rings and dust
  • Planetary Sciences: Solar System Objects: Planetary rings
  • Planetary Sciences: Solar System Objects: Saturn

Abstract

Cassini observations of the thermal plasma in the vicinity of Saturn's main rings and the F and G rings

R. L. Tokar

Space Science and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico, USA

R. E. Johnson

Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia, USA

M. F. Thomsen

Space Science and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico, USA

D. M. Delapp

Space Science and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico, USA

R. A. Baragiola

Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia, USA

M. F. Francis

Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia, USA

D. B. Reisenfeld

Department of Physics and Astronomy, University of Montana, Missoula, Montana, USA

B. A. Fish

Department of Physics and Astronomy, University of Montana, Missoula, Montana, USA

D. T. Young

Southwest Research Institute, San Antonio, Texas, USA

F. J. Crary

Southwest Research Institute, San Antonio, Texas, USA

A. J. Coates

Mullard Space Science Laboratory, University College London, Surrey, UK

D. A. Gurnett

Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA

W. S. Kurth

Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, USA

The ion mass spectrometer on Cassini detected enhanced ion flux near Saturn's main rings that is consistent with the presence of atomic and molecular oxygen ions in the thermal plasma. The ring “atmosphere” and “ionosphere” are likely produced by UV photosputtering of the icy rings and subsequent photoionization of O2. The identification of the O+ and O2 + ions is made using time-of-flight analysis and densities and temperatures are derived from the ion counting data. The ion temperatures over the main rings are a minimum near synchronous orbit and increase with radial distance from Saturn as expected from ion pick up in Saturn's magnetic field. The O2 + temperatures provide an estimate of the neutral O2 temperature over the main rings. The ion mass spectrometer also detected significant O2 + outside of the main rings, near the F ring. It is concluded that between the F and G rings, the heavy ion population most likely consists of an admixture of O2 + and water group ions O+, OH+, and H2O+.

Received 11 February 2005; accepted 16 May 2005; published 11 June 2005.

Citation: Tokar, R. L., et al. (2005), Cassini observations of the thermal plasma in the vicinity of Saturn's main rings and the F and G rings, Geophys. Res. Lett., 32, L14S04, doi:10.1029/2005GL022690.

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