Although there are, in addition to the classic but somewhat dated books'l-, some excellent recent books on ionospheric physics and aeronomy'l-..., their scope is quite different from that of the present monograph. This monograph concentrates on the fundamental physical and chemical processes in an idealized planetary ionosphere as a general abstraction, with actual planetary ionospheres representing special cases. Such an approach appears most appropriate for a concise in troduction to the field, at a time when increasing experimental in formation on the ionospheres of other planets can be...