Planetary rings

The individual ring systems are described with dust/magnetosphere interactions high-lighted somewhat. Jupiter's main ring is tenuous and enveloped by the magnetosphere; it principally contains micron-sized silicate grains. A vertically-extended, radially-localized “halo” of submicron particles lies inward of the main ring while a newly-discovered very faint ring lies outside it. The classical Saturnian system is composed of water ice chunks with sizes principally between cm and meters. Satellite resonances determine some ring structure but most is not understood. The faint exterior rings (E, G, F and one just identified between the A and F rings) are intimately associated with magnetospheric particles and contain mainly small grains, which are also prominent in the “spokes” located in the dense, middle portion of the B ring. Most of the nine narrow Uranian rings are slightly inclined and eccentric, and presumably lie within the putative Uranian magnetosphere. Particles are likely carbonaceous; sizes are thought to be larger than microns.