00-048

Cover Page/Proposal Summary

ROSS-99    NRA 99-OSS-01

Date Due: 5/3/99

NASA PROCEDURE FOR HANDLING PROPOSALS

This proposal shall be used and disclosed for evaluation purposes only, and a copy of this Government notice shall be applied to any reproduction or abstract thereof. Any authorized restrictive notices that the submitter places on this proposal shall also be strictly complied with. Disclosure of this proposal for any reason outside the Government evaluation purposes shall be made only to the extent authorized by the Government.

Proposal Type: New Proposal

Proposal Category: Atmosphere Structures and Particles

Major Equipment Proposal? No

Do you intend to submit an Education/Public Outreach (E/PO) proposal? Yes

Proposal Title:
Io and its plasma torus: Atmosphere-magnetosphere interactions

Abbreviated Proposal Title:
Io and its plasma torus

Principal Investigator:
Dr. Floyd Herbert
Lunar And Planetary Lab - West
University of Arizona
901 Gould-Simpson Building
1040 E. 4th Street
Tucson, AZ 85721-0077
Phone: 520-621-4569   Fax: 520-621-8364   E-mail: herbert@argus.lpl.arizona.edu

SignatureDate
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Co-Investigators and Collaborators:
Type    Name    Affiliation    E-mail
Sci Collab   Dr. A. L. Broadfoot   U. of Arizona   lyleb@argus.LPL.arizona.edu
Sci Collab   Dr. Bill R. Sandel   U. of Arizona   sandel@argus.LPL.arizona.edu
Sci Collab   Dr. G. Randall Gladstone   SW Research Inst.   randy@whistler.space.swri.edu


Proposal Summary:

OBJECTIVES: We seek to understand atmosphere-magnetosphere interactions. Topics we will investigate include the energy transport in the Io plasma torus, which is a ring of plasma in the Jovian magnetosphere, and the interaction produced when this plasma impinges on the tenuous atmosphere of Io, Jupiter's volcanic moon. METHODS: We will exploit a combination of data analysis and theory. We will use extreme ultraviolet (EUV) observations of the torus by UVSTAR and EUVE (both are EUV spectrographic telescopes in low Earth orbit) in order to measure the electron temperature distribution, fluctuation spectrum, and mass-temperature relation in the torus. We will compute models of the electrodynamic interaction between the plasma wind and Io's atmosphere, with primary emphasis on self-consistency between the modification of the atmosphere by the plasma and the deviation of the plasma flow by the atmosphere. SIGNIFICANCE: Jupiter's magnetosphere is a natural plasma physics lab that can be observed both remotely and in situ, so that it are a unique opportunity for learning more about both plasma physics and remote astrophysical phenomena. These processes, generally, are important for understanding the evolution of planetary and satellite atmospheres. The results of our study will be useful in interpreting data to be returned from the Galileo and Cassini missions. ACCOMPLISHMENTS OF PRIOR WORK: We have determined the 3-dimensional structure of the Io plasma torus during the Voyager 1 flyby, constraining mass and energy sources (preprint appended). We have discovered that the fluctuating Io torus electron density and temperature are anti-correlated, constraining the nature of the torus power source (JGR 103:19,915 1998). EDUCATION PROPOSAL SUMMARY: We will create an educational World-Wide Web site for middle- and high-school students. We will provide graphic aids, including animated diagrams, to facilitate site-visitor visualization of the processes discussed.