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The Atmosphere of Io: Abundances and Sources of Sulfur Dioxide and Atomic Hydrogen

  • Darrell F. Strobel
  • Brian C. Wolven
Conference paper

Abstract

An analysis and interpretation of reflected solar Lyman α intensity data acquired with the Hubble Space Telescope (HST) implies an equatorially confined atmosphere with SO2 column densities ∼ 1−2 × 1016 cm−2. Poleward of 30° the SO2 density must decrease sharply reaching an asymptotic polar value of < 1015 cm−2 at 45° to achieve the observed 2 kR intensity peaks. The corresponding surface reflectivities must be either a constant 0.047 for higher equatorial SO2 or a variable reflectivity of 0.027 with lower SO2 densities at the equator increasing to a polar value of ∼ 0.05. The average residence time for an atmospheric SO2 molecule is ∼ 2–3 days for the canonical mass loading rate of the Io plasma torus = 1030 amu s−l. With atomic hydrogen in the atmosphere and corona constrained by the HST observations, it is estimated that a pickup proton density ratio of 0.25–0.4% can be sustained by a supply of Io plasma torus protons neutralized in Io’s atmosphere/exosphere, if protons constitute 7% of the total torus ion density, which is close to the Chust et al. (1999) pickup proton density ratio and under the widely quoted 10% proton content of the torus.

Keywords

Column Density Hubble Space Telescope Geometric Albedo Pickup Proton Charge Exchange Cross Section 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 2001

Authors and Affiliations

  • Darrell F. Strobel
    • 1
    • 2
  • Brian C. Wolven
    • 2
  1. 1.Department of Earth and Planetary SciencesThe Johns Hopkins UniversityBaltimoreUSA
  2. 2.Department of Physics and AstronomyThe Johns Hopkins UniversityBaltimoreUSA

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