Analytic study on the location of mode conversion at lower-hybrid resonance

An analytic method based on asymptotic series expansion is introduced to determine the location of mode conversions at lower-hybrid resonance. Because of simple analytic expression for turning points, the condition of three categories of disappearance of mode conversion is obtained with clear physical reasons. An example on the lower-hybrid wave mode conversion in inhomogeneous Tokamak plasma is studied in detail. (author)