Abstract/Details

Sodium in Io's extended atmosphere


1988 1988

Other formats: Order a copy

Abstract (summary)

This dissertation combines several new observations of the Io sodium cloud to create a consistent picture of the extended Io atmosphere and its interaction with the Jovian plasma torus. I used the LPL echelle spectrograph to obtain three types of high-resolution spectra of the extended sodium cloud at the sodium D-lines (5890, 5896A). The first class of observations made use of the mutual satellite eclipses of 1985 to probe the density profile of the atmosphere in the range 1.4 to 10 Io radii, a previously unstudied region. The second type of observation examined the sodium emission in Io's immediate vicinity, allowing an accurate measurement of the velocity structure around Io. The final method employed a high-sensitivity detector to study faint jets of high-speed sodium farther out in the extended cloud. The synthesis of these three data sets results in a better understanding of how sodium is distributed about Io as a function of position and velocity.

Io's extended atmosphere is composed of many kinematically distinct components. The distribution in space is linked to their characteristic velocities, with low-energy sodium confined near Io and faster atoms (10 to 100 km sec$\sp{-1}$) prevalent beyond $\sim$25 Io radii. The sodium density profile is steep near Io and shallower outside 5.6 Io radii, the effective limit of Io's gravity.

The data indicate that the atmosphere is collisionally thick near the surface, but becomes thin by an altitude of $\sim$700 km. The upper limit of the exobase location is derived from reliable sodium density measurements made during the satellite eclipses. The lower limit is indirectly inferred from the velocity distribution of sodium near Io and the nature of high-speed jets far from Io.

The high-speed sodium jets reveal a new type of close interaction between the corotating plasma and Io's atmosphere. The morphology and brightness of the jets require a two-reaction process, in which atmospheric sodium is ionized, accelerated to high speeds, and then charge-exchanges with other sodium atoms. These processes must occur near the atmospheric exobase, indicating that Io's atmosphere is not completely protected from the plasma flow.

Indexing (details)


Subject
Astronomy;
Astrophysics
Classification
0606: Astronomy
0606: Astrophysics
Identifier / keyword
Pure sciences
Title
Sodium in Io's extended atmosphere
Author
Schneider, Nicholas McCord
Number of pages
219
Publication year
1988
Degree date
1988
School code
0009
Source
DAI-B 49/05, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Advisor
Hunten, Donald M.
University/institution
The University of Arizona
University location
United States -- Arizona
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
8814275
ProQuest document ID
303687421
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/303687421
Access the complete full text

You can get the full text of this document if it is part of your institution's ProQuest subscription.

Try one of the following:

  • Connect to ProQuest through your library network and search for the document from there.
  • Request the document from your library.
  • Go to the ProQuest login page and enter a ProQuest or My Research username / password.