On the magnetospheres of Jupiter, Saturn, and Uranus

A brief descriptive summary of Jupiter's magnetosphere is based on in situ observations with the spacecraft Pioneer 10 and Pioneer 11 in November-December 1973 and November-December 1974, respectively. Current interpretative work emphasizes particle acceleration and loss mechanisms, the determination of diffusion coefficients by satellite effects, the topology of the outer magnetosphere, the possible recirculation of energetic particles, and the controversial evidence for an extended magnetotail. Available evidence on non-thermal radio emissions of Saturn and on the solar wind flow at 10 AU is invoked to suggest that Saturn very likely has a large, well developed magnetosphere resembling that of Jupiter but with the important difference that a radiation belt can not exist interior to the outer edge of the A ring of particulate matter. The first in situ observations will be made by Pioneer 11 in August-September 1979. In the context of present knowledge it is speculated that Uranus also has a large, well developed magnetosphere and one of unique interest during epochs when its rotational axis is approximately along the planet-sun line as in mid-1985. On of the two-planned Mariner Jupiter Saturn missions may be targeted so as to fly by Uranus in 1986. (Auth.)