Types of planetary tori

A satellite torus is a fixed planetary feature made out of a mixture of ions and neutrals in temporary residence. The parent satellite supplies matter constantly to maintain the torus against continuous losses. As fixed planetary features, one torus is like another in that any one depicts the group. But as features in dynamic balance between production and loss, there are qualitatively different types of tori. One type does not depict the others. The differences show up in how they respond to perturbations away from their equilibrium ion and neutral densities. Most are stable, some are not, and some have no equilibria. The stable types take different paths back to equilibrium. The types arise as follows. There are two kinds of processes that can put satellite material into the torus. In one, the torus is an active scavenger; in the other, it is a passive receiver. And there are three kinds of processes that can remove material from the torus: (1) recombination, which produces fly-away neutrals, (2) ion outflow in which the torus plays an active part, or (3) ion outflow in which the torus plays a passive part. Thus there are six combinations of source types and loss types. In addition, one loss type has a stable and an unstable regime. This paper describes the equilibrium and dynamical properties of the possible torus types. We attempt to classify the known solar system examples. Not all types exist.