Wigner’s Function Method for Describing Linear Conversion of Electromagnetic Waves in Overdense Gyrotropic Plasma

Abstract A general method for accounting for the effect of electromagnetic wave tunneling through the evanescent region in inhomogeneous magnetized plasma within the ray kinetic equation framework (Weyl formalism, method of Wigner functions) is developed. The proposed approach is based on analytical solutions of reference Maxwell’s equations in a vicinity of the linear mode coupling region and preserves the main numerical advantage of the kinetic equation method—the ability to calculate all rays independently. The method is adapted to describe the linear mode coupling (conversion of the ordinary and extraordinary waves) in the vicinity of plasma cutoffs in toroidal plasmas, which is important for modeling microwave heating of overdense hot plasmas in tokamaks. An example of numerical calculation of the linear conversion of microwave radiation in a tokamak plasma using the new method is given.