Parametric instabilities and electrostatic ion-cyclotron waves in multispecies plasmas

An introduction is given to the analysis of the cyclotron decay instability in which the reasons for studying the instability and the basic plasma model used for the calculations are discussed. The important physical features of the instability determined in subsequent portions of this work are summarized. Parametric instabilities excited by a magnetosonic pump wave in an infinite, homogeneous, multispecies plasma are considered. A general formalism for studying waves propagating in a plasma with density and magnetic field gradients is discussed. Specializing to electrostatic ion-cyclotron waves propagating nearly perpendicular to the gradients, it is shown that density gradients can lead to local or nonlocal structure around points where the relative density gradient, N'/N, has a local maximum or minimum. The presence of magnetic field gradients results in the convection of wave energy in the direction of increasing field strength. Application of the formalism to the cyclotron decay instability is discussed. In particular, it is concluded that density and magnetic field gradients should not be critical to the development of the instability in the FM-1, ATC, and PLT devices of Princeton. Various weak turbulence processes are considered as possible means of saturating the cyclotron decay instability and heating the ions in homogeneous plasmas