Variational theory of the cyclotron-emission source distribution from a mode-conversion layer

This paper presents the theory of an inhomogeneous source of cyclotron emission from a three-branch mode-conversion layer in a non-uniformly magnetized plasma. The physical formulation of the problem is based on the generalized Kirchhoff's law that relates, branch by branch, the emission to the absorption. General integral expressions for both absorbed and emitted energy fractions along each wave branch are obtained. A discrete multi-point model of absorbers and emitters is analysed. A variational principle for the integral of the emitted power is formulated.