Open AccessModeling temporal variability of plasma conditions in the Io torus during the Cassini era
Author(s) -
Delamere P. A.,
Steffl A.,
Bagenal F.
Publication year - 2004
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2003ja010354
Subject(s) - torus , plasma , physics , atmospheric sciences , electron , electron temperature , mixing ratio , ion , homogeneous , ultraviolet , environmental science , extreme ultraviolet , astrophysics , atomic physics , thermodynamics , nuclear physics , laser , mathematics , geometry , quantum mechanics , optics
Observations of ultraviolet (UV) emissions from the major ion species (S + , S ++ , S +++ , O + , O ++ ) of the Io plasma torus made during the Cassini flyby (October 2000 to March 2001) have revealed significant time variability. Using a homogeneous model for mass and energy flow in the torus parameterized by five input variables (transport timescale, neutral source strength, ratio of oxygen to sulfur atoms in the source, fraction of superthermal electrons, and temperature of the hot electrons), we have investigated the time variability of the torus properties (density, composition, and temperature) during the Cassini era. In order to match the changes in emissions, the model suggests that a significant change in the neutral source occurred near the beginning of the observing period, decreasing from >1.8 tons/s to 0.7 tons/s. The changes in the neutral source appear to coincide with the declining phase of a dramatic (i.e., 2–3 order of magnitude) peak in iogenic dust emissions observed by Galileo prior to the Cassini era.