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Radial diffusion in Io's torus: Some implications from Voyager I
Author(s) -
Froidevaux Lucien
Publication year - 1980
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl007i001p00033
Subject(s) - physics , diffusion , orbit (dynamics) , steady state (chemistry) , ion , torus , radial velocity , atomic physics , plasma diffusion , astrophysics , electron density , electron , computational physics , nuclear physics , thermodynamics , stars , chemistry , geometry , mathematics , quantum mechanics , engineering , aerospace engineering
Data from several Voyager 1 experiments are used to determine the magnitude and L dependence of the radial diffusion coefficient for low‐energy charged particles outside of Io's orbit under steady‐state conditions. The extreme ultraviolet observations near 685Å are inverted to produce an ion density profile for L > 6. This normalized ion profile, as well as the (equatorial) electron density profile estimated from the planetary radio astronomy (PRA) observations falls off as L −5 . Such a density gradient would make possible centrifugally driven cross‐L diffusion outside of Io's orbit without ruling out the presence of an atmospherically driven mechanism. A lower limit for the radial diffusion coefficient D LL is 1.5 × 10 −10 L 5 R J ² sec −1 , yielding a characteristic diffusion time from 6R J to 7R J of less than 10 days, much shorter than previously anticipated. Steady‐state diffusion is not a good assumption inside of Io's orbit, where the particle densities decrease sharply from 6R J to 5R J ; the diffusion time in that region is probably longer than outside of Io's orbit.