Magnetosphere-Ionosphere Coupling At Planets And Satellites

An important topic in solar system plasma physics is the linkage and coupling of denser, colder ionospheric plasma of planets and satellites with more energetic external plasma such as in the solar wind, magnetospheres, and ionospheres. How energy and momentum are exchanged between different plasma regions obviously depends on the characteristics of the body, and in particular on the presence of, or lack of, a significant intrinsic magnetic field. Field-aligned electrical currents play an important role in these processes. The strong magnetic fields at Earth, Jupiter, and Saturn carve out large magnetospheres, within which the electrodynamical force balance is enforced by current systems, some of which close in the ionosphere. Auroral emission from planetary or satellite upper atmospheres often, but not always, accompanies the field-aligned currents. Objects like Venus, and Saturn's satellite Titan, have ionospheres, but lack significant intrinsic magnetic fields. The external plasma, solar wind plus associated induced magnetospheres, still couples with the ionospheres and upper atmospheres of such bodies. A broad review of magnetosphere-ionosphere (M-I) coupling at other planets will be given in this chapter.