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The source location of certain Jovian decametric radio emissionsEvidence is presented which supports the concept that certain of the Jovian decametric radio waves originate as northern hemisphere extraordinary mode cyclotron emissions. The wave signals received by Voyager 1 near 10 MHz shortly after the closest approach to Jupiter were found to exhibit cusps in the fringe pattern which can be attributed to Faraday rotation in the Io plasma torus. At nearly the same time, the wave polarization near 1 MHz was found to exhibit a sudden reversal of its rotation sense, indicating that the wave path for those frequencies had also become perpendicular to the magnetic field at the spacecraft. It was determined that the waves came from the northern hemisphere at progressively lower altitudes with increasing frequency, and if the source is assumed to be associated with an L = 6 field line, the emission appears to have occurred near the source cyclotron frequency somewhere in the local midnight sector. The evidence indicates that the source is at the Io flux tube and that the emitted wave mode must have been extraordinary. In addition, the emitted wave polarization must have been substantially noncircular which would require a low plasma density near the source, much like that which occurs with auroral kilometric radiation at the earth.
Document ID
19830061190
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Calvert, W.
(Iowa, University Iowa City, IA, United States)
Date Acquired
August 11, 2013
Publication Date
August 1, 1983
Publication Information
Publication: Journal of Geophysical Research
Volume: 88
ISSN: 0148-0227
Subject Category
Lunar And Planetary Exploration
Accession Number
83A42408
Funding Number(s)
CONTRACT_GRANT: NAGW-256
CONTRACT_GRANT: NGL-16-001-043
Distribution Limits
Public
Copyright
Other

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