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The Mimas ghost revisited - An analysis of the electron flux and electron microsignatures observed in the vicinity of Mimas at SaturnAn analysis of the electron-absorption signature observed by the cosmic-ray system on Voyager 2 near the orbit of Mimas is presented. It is found that these observations cannot be explained as the absorption signature of Mimas. By combining Pioneer 11 and Voyager 2 measurements of the electron flux at Mimas's orbit (L = 3.1), an electron spectrum is found in which most of the flux above about 100 keV is concentrated near 1 to 3 MeV. This spectral form is qualitatively consistent with the bandpass filter model of Van Allen et al. (1980). The expected Mimas absorption signature is calculated from this spectrum neglecting radial diffusion. Since no Mimas absorption signature was observed in the inbound Voyager 2 data, a lower limit on the diffusion coefficient for MeV electrons at L = 3.1 of D greater than 10 to the -8th sq Saturn radii/sec is obtained. With a diffusion coefficient this large, both the Voyager 2 and the Pioneer 11 small-scale electron-absorption-signature observations in Mimas's orbit are enigmatic. Thus the mechanism for producing these signatures is referred to as the Mimas ghost. A cloud of material in orbit with Mimas may account for the observed electron signature if the cloud is at least 1-percent opaque to electrons across a region extending over a few hundred kilometers.
Document ID
19840030076
Document Type
Reprint (Version printed in journal)
Authors
Chenette, D. L. (Aerospace Corp. Los Angeles, CA, United States)
Stone, E. C. (California Institute of Technology Pasadena, CA, United States)
Date Acquired
August 12, 2013
Publication Date
November 1, 1983
Publication Information
Publication: Journal of Geophysical Research
Volume: 88
ISSN: 0148-0227
Subject Category
LUNAR AND PLANETARY EXPLORATION
Funding Number(s)
CONTRACT_GRANT: NAS7-918
CONTRACT_GRANT: NGR-05-002-160
Distribution Limits
Public
Copyright
Other