On the theory of wave conversion in inhomogeneous plasma

Wave conversion in a one-dimensionally inhomogeneous plasma described by a differential equation of th the fourth order in case of a weak inhomogeneity is theoretically studied. The analytical expressions for the electric field intensity in the conversion region in terms of the Airy function asymptotically connected while moving away from the conversion region with solutions determined by the WKB approximation method are obtained. The results obtained are used for estimation of the electric field amplitude and the role of parametric instabilities on HF plasma heating in great toroidal traps (the regions of lower, ion-ionic and upper hybrid resonances are considered)