Saturation of the parametric instability of ion-cyclotron oscillations in a plasma with an ion temperature anisotrophy

In this paper we study turbulent fluctuations and evaluate the effective collision frequency in the region above the threshold for decay of a lower-hybrid pump into lower-hybrid and ion-cyclotron waves in a plasma with an ion temperature anisotropy. The pump wave field is assumed to be weak, so that we have νE/νe << 1, where νE = eE0/meω0 is the quiver velocity of the electrons in the pump wave field E0 and νeTe/me1/2 is their thermal velocity. The action of this field can give rise to parametric instabilities, but over the time during which these instabilities develop the degree of ion temperature anisotropy can be regarded as fixed. The threshold field strength is found as a function of the anisotropy of the ion component of the plasma. In order to describe the saturation of the parametric instability of ion-cyclotron oscillations we have invoked a nonlinear mechanism resulting from scattering of charged particles by turbulent fluctuations of the electric field and have calculated the effective collision frequency νeff. We conclude that the resulting anisotropy of the ion temperature can be used as a plasma diagnostic