Abstract
Abstract. The Voyager 1 outbound ultraviolet observations of the Io plasma torus are used to determine the location of the ansae, to obtain a third viewing angle of this structure in the Jovian magnetosphere. At an angle of -114∘ with respect to the Sun–Jupiter line, or a Jovian local time of 04:30 LT, the Voyager 1 data deliver a distance of 5.74±0.10 RJ for the approaching and 5.83±0.15 RJ for the receding ansa. Various periodicities in the radial distance, brightness and width of the ansae are seen with respect to system III longitude and Io phase angle. The torus ribbon feature does not appear in all ansa scans. Keywords. Magnetospheric physics (magnetosphere interactions with satellites and rings)
Highlights
The Io plasma torus is a gaseous cloud centred at Jupiter, basically located at Io’s orbit
It is clear that the simple brightness model including a ribbon feature fits some of the ansae rather well; there are clear cases in which the this model is inadequate
Voyager 1 outbound ultra-violet observations of the Io plasma torus have given a new viewpoint of this interesting structure in the Jovian magnetosphere
Summary
The Io plasma torus is a gaseous cloud centred at Jupiter, basically located at Io’s orbit. It consists mainly of sulfur and oxygen, which is created by Io’s volcanic activity and has an input rate of approximately 1 tonne per second. The torus was first discovered by Kupo et al (1976) and later many spacecraft (e.g. Pioneer 10, Voyager 1 and 2, Galileo and Cassini) and ground-based and space telescopes have observed this object. The main emission region seemed to be very small, where an estimated 85 % of the UV emission appeared to come from a narrow ribbonlike structure in the torus (just inside of Io’s orbit) not wider than 0.2 RJ (Dessler and Sandel, 1993)
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