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Low-energy charged particle environment at jupiter: a first look
Science (New York, N.Y.)
|June 1, 1979
Summary
Voyager
Area of Science:
- Planetary Science
- Plasma Physics
- Space Physics
Background:
- The Voyager spacecraft's low-energy charged particle instrument was designed to study Jupiter's magnetosphere.
- Previous theories suggested planetary wind outflow from Jupiter's magnetosphere.
Purpose of the Study:
- To measure the hot plasma component of Jupiter's magnetosphere.
- To investigate the composition, temperature, density, and dynamics of this plasma.
- To compare observations with existing theories of magnetospheric outflow.
Main Methods:
- Utilized the Voyager low-energy charged particle instrument to detect electrons and ions.
- Analyzed particle energies, composition, temperature, density, and energy density.
- Tracked particle flux variations with longitude and time during inbound and outbound trajectories.
Main Results:
- Detected hot plasma (15-30 keV electrons, 30+ keV ions) nearly 0.3 AU from Jupiter.
- Identified plasma composition as primarily protons, oxygen, and sulfur, with a nonthermal tail.
- Observed plasma corotation, with no evidence of planetary wind outflow.
- Energetic particles (>200 keV/nucleon) included protons, helium, oxygen, sulfur, and sodium, likely originating from Io.
- Observed longitudinal flux enhancements and 5- and 10-hour periodicities on the outbound trajectory.
- Detected partial absorption of high-energy electrons near the Io flux tube.
Conclusions:
- Jupiter's hot plasma is largely corotating and does not exhibit significant outflow.
- Io is a probable source for several energetic particle species in the outer magnetosphere.
- Magnetospheric dynamics show longitudinal variations and temporal periodicities, particularly on the outbound path.
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