VLF receiving directivity pattern of electric and magnetic dipoles in magnetoactive plasma

Abstract

The directivity of receiving electric and magnetic VLF dipoles in a magnetoactive environment is characterized by the ratio of the output e.m.f. modulus to field strength modulus of the corresponding wave component or in other words, the modulus of a quantity proportional to the effective length. The antenna patterns with regard to a plane monochromatic wave are analyzed in terms of the dipole orientation in the steady magnetic field B ̄ o and the direction of wave propagation. The antenna patterns are symmetrical figures whose symmetry axes (zero directions) coincide with the direction of the wave vector for the magnetic dipole and with the normal to thee-plane of the wave in which the E ̄ polarization ellipselies for the electric dipole. The E ̄ vector and the normal to the e-plane in a magnetoactive environment possess different orientations with respect to the magnetic field as, accordingly, do the antenna patterns of the electric and the magnetic dipole. In a magnetoactive plasma the antenna patterns differ from those in an isotropic medium due to different wave field structures in these media. In random fields the minima of the antenna patterns are well pronounced even if the wave vector orientation shows considerable fluctuations (up to ± 20°).