ABSTRACT
In this section, we present a relatively simple, yet very useful, model for the dynamics of fully ionized plasmas, as they are found in, for instance, the Earth’s upper ionosphere, in the magnetosphere or in the more distant regions of space. The model is based on some simple assumptions, by arguing that a plasma can be considered as a medium which follows the same basic laws as any other continuum, i.e., the equation of continuity, Newton’s second law. The electromagnetic parts of the Àelds that are entering the total force have to be consistent with Maxwell’s equations, subject to some simpliÀcations, which are valid within certain parameter regions. The model ignores the fact that a plasma is composed by a mixture of two “gases,” an electron and an ion “gas.” Instead the plasma is described as one medium, characterized essentially by its large conductivity, but we do not here address the question how this conductivity is achieved!
