Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-08-01
Icarus 180 (2006) 124-140
Astronomy and Astrophysics
Astrophysics
35 pages including 12 figures and 2 tables
Scientific paper
10.1016/j.icarus.2005.07.013
In this third paper in a series presenting observations by the Cassini Ultraviolet Imaging Spectrometer (UVIS) of the Io plasma torus, we show remarkable, though subtle, spatio-temporal variations in torus properties. The Io torus is found to exhibit significant, near-sinusoidal variations in ion composition as a function of azimuthal position. The azimuthal variation in composition is such that the mixing ratio of S II is strongly correlated with the mixing ratio of S III and the equatorial electron density and strongly anti-correlated with the mixing ratios of both S IV and O II and the equatorial electron temperature. Surprisingly, the azimuthal variation in ion composition is observed to have a period of 10.07 hours--1.5% longer than the System III rotation period of Jupiter, yet 1.3% shorter than the System IV period defined by Brown (1995). Although the amplitude of the azimuthal variation of S III and O II remained in the range of 2-5%, the amplitude of the S II and S IV compositional variation ranged between 5-25% during the UVIS observations. Furthermore, the amplitude of the azimuthal variations of S II and S IV appears to be modulated by its location in System III longitude, such that when the region of maximum S II mixing ratio (minimum S IV mixing ratio) is aligned with a System III longitude of ~200 +/- 15 degrees, the amplitude is a factor of ~4 greater than when the variation is anti-aligned. This behavior can explain numerous, often apparently contradictory, observations of variations in the properties of the Io plasma torus with the System III and System IV coordinate systems.
Bagenal Fran
Delamere Peter A.
Steffl Andrew J.
No associations
LandOfFree
Cassini UVIS Observations of the Io Plasma Torus. III. Observations of Temporal and Azimuthal Variability does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Cassini UVIS Observations of the Io Plasma Torus. III. Observations of Temporal and Azimuthal Variability, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cassini UVIS Observations of the Io Plasma Torus. III. Observations of Temporal and Azimuthal Variability will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-615172