ABSTRACT
Plasma media can support a rich variety of instabilities. Some of these are to be considered as relatively straightforward generalizations of instabilities known in neutral Áuids; others are speciÀc for plasmas, the kinetic instabilities in particular. One might attempt a separate description of Áuid and kinetic instabilities, as done in the following, but strictly speaking, such a separation is futile since, for instance, a separate Áuid description of electrons and ions is feasible only for plasmas. We will here adopt the distinction that, provided the basic equation is a one or two Áuid model for ions and electrons, the instabilities will be considered “Áuid-like,” and kinetic instabilities otherwise. Instabilities termed Áuid-like here, will of course be found also in a kinetic description, but often at the expense of a more complicated analysis. There are, on the other hand, instabilities which are only found in kinetic descriptions. Instabilities are mostly found in linearized descriptions, apart from a few nonlinear instabilities occurring in linearly stable plasmas. Instabilities can occur in magnetized or unmagnetized plasmas, but it will be somewhat clumsy to make a subdivision in a short summary as the one attempted in the following.
