On the distribution of the field of electromagnetic waves emitted by a dipole in a homogeneous magnetoactive plasma

Abstract

This paper deals with the emission of an electric dipole in a homogeneous magneto-active multicomponent plasma in all resonance frequency ranges ω which are lower than the Langmuir electron frequency ω 0. We show that the structure of the field represents two cones, one inserted into the other with the common symmetry axis along the vector of the magnetic field H ̄ 0 . The surface of one of them corresponds to the plasma resonance region. The other is an analogue of Storey's cone in the whistler mode range. In the vicinity of the surfaces of these cones and near the symmetry axis, in a narrow range of angle, a considerable amplification of the field can take place. In some cases the maximum value of the field strength exceeds the field inside the cones, and the field of a similar dipole located in vacuum, by approximately (10 1–10 5) times. This effect is considerable and must play a prominent part in various processes taking place in a plasma. The emission energy is redistributed with distance from the source: initially the maximal field strength is near the surface of the resonance cone, but starting from near the symmetry axis i.e. at sufficiently large distances, the field energy is concentrated along the magnetic line of force passing through the source. Asymptotic formulae are obtained for all the regions inside and outside the cones. The results of the numerical calculations characterizing the spatial field pattern and its change as a function of frequency are given for the whistler mode.