The linear mode conversion regime for the approximate dispersion relation [ω−ω1
)]=η occurs near x
such that ω1
). Cairns and Lashmore‐Davies [Phys. Fluids 25
, 1605 (1982); 26
, 1268 (1983)] have recently expressed the associated energy flow in terms of a single parameter that involves η and the partial derivatives of ω1
. In this paper, a different, wave‐mechanical approach is used to obtain the same result. The process of linear mode conversion is discussed using the system
is a Hermitian operator. The degeneracy of plasma modes, and their coupling by warm plasma corrections in an inhomogeneous plasma, is dealt with using first‐order perturbation theory. Simple coupled first‐order differential equations for the wave amplitudes follow, which can be integrated directly. The calculated energy flow reproduces the expression that is obtained from the theory of Cairns and Lashmore‐Davies.