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Periodic variations in Io's sodium and potassium cloudsSpectra of Io's sodium cloud taken 7.5 to 45 sec north and south of Io at a variety of magnetic latitudes of Io obtained during 17 nights of the 1975 apparition of Jupiter confirm the weakening of the cloud in the neighborhood of Jupiter's magnetic equator. The time scale for these changes is 1.5 hours or less. For impact ionization to cause these changes, a minimum flux of 100 billion/sq cm/sec 15 eV electrons or 40 billion/sq cm/sec 8 keV protons is required. Sodium velocities near 10 km/sec are required to explain the replenishment of ionized regions of the cloud. We also obtained spectra of Io's potassium cloud on eight nights during the 1975 apparition. This cloud appears to behave like the sodium cloud as Io's magnetic latitude varies. The potassium, however, may become much weaker as Io passes through the magnetic equator. The brightest intensity measured for the 7665 A resonance line was about 1 kR at a point 7.5 sec east of Io.
Document ID
19770059502
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Trafton, L.
(McDonald Observatory; Texas, University Austin, Tex., United States)
Date Acquired
August 9, 2013
Publication Date
August 1, 1977
Publication Information
Publication: Astrophysical Journal
Subject Category
Lunar And Planetary Exploration
Accession Number
77A42354
Funding Number(s)
CONTRACT_GRANT: NGR-44-012-152
Distribution Limits
Public
Copyright
Other

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