Passage through Io's ionospheric plasmas by the Galileo spacecraft

Details Passage through Io's ionospheric plasmas by the Galileo spacecraft Passage through Io's ionospheric plasmas by the Galileo spacecraft

Nov 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001jgr...10626209f&link_type=abstract

Journal of Geophysical Research, Volume 106, Issue A11, p. 26209-26224

Physics

12

Magnetospheric Physics: Magnetosphere Interactions With Satellites And Rings, Planetology: Fluid Planets: Tori And Exospheres, Planetology: Solar System Objects: Jovian Satellites, Planetology: Solar System Objects: Jupiter

Scientific paper

On February 22, 2000, the Galileo spacecraft passed by the moon Io at a closest approach distance of 206 km. This altitude was sufficiently low that the plasma analyzer observed the three-dimensional ion velocity distributions as functions of energy/charge (E/Q) at the top of Io's ionosphere. The ionospheric ion distributions consisted of two populations, a warm distribution with density and temperature of ~8000 cm-3 and 10,000 K and a cool population with 3000 cm-3 and 2300 K. This cooler temperature is in the range of those observed remotely for some volcanic plumes. The bulk speed of these ions was 2 km s-1 with respect to Io's surface. In order to identify the mass/unit charge (M/Q) of the ionospheric ions, the E/Q spectra of the pickup ions in this region were examined. The most probable M/Q of the primary population of these ions was inferred to be 64. Remote spectroscopic observations of Io's surface and atmosphere suggest that these ions are S2+ and/or SO2+, although SO+ and SO3+ are not eliminated as possibilities. There is some evidence for lesser densities of heavier ions such as S3+ and S4+. The densities, temperatures, and bulk flow velocities of torus ions were measured as the spacecraft approached Io from the upstream direction. A combination of fits to the E/Q spectra observed with Galileo, the determinations of the M/Q of the primary ions with the plasma instrumentation on this spacecraft during other passages, and the previous identification of the primary ions with Voyager 1 plasma and remote observations find the following primary composition for the unperturbed torus near Io: O++ (50 cm-3, 30 eV), O+ (200 cm-3, 30 eV), S++ (400 cm-3, 90 eV), and S+ (100 cm-3, 90 eV). At a radial distance from Io of ~19,700 km (10.9 Io radii), changes in the torus ion density, temperature, and bulk flow velocity provide evidence that a cloud of neutral gases is co-orbiting with Io and is providing a substantial interaction with the torus ions.

Affiliated with

Also associated with

No associations

Rating

Passage through Io's ionospheric plasmas by the Galileo spacecraft 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 Passage through Io's ionospheric plasmas by the Galileo spacecraft, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Passage through Io's ionospheric plasmas by the Galileo spacecraft will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1555627