Near-Field of a VLF Electric Dipole in an Anisotropic Plasma

In this paper, we proposed a semianalytical method for evaluating the near-zone field of a very low frequency (VLF) electric dipole in a homogeneous and anisotropic plasma. Due to the different attenuation properties for the ordinary wave (O-wave) and the extraordinary wave (E-wave), the integrals corresponding to their contributions should be truncated at different locations of the real axis and need to be separately treated. By applying the complex function theory and a speed-up convergence algorithm, the original oscillating integral for the near-field is transformed into two fast convergent integrals plus an analytical solution. Computations show that, in the near zone, the O-wave still has comparable amplitudes with the E-wave, and its influence on the total field should not be neglected. It is also observed from the radiation pattern that there exists a pronounced "cohesion effect" for the E-wave along the direction of the geomagnetic field, while the phase mutations of the O-wave exactly coincide with the minima of its field strength. Moreover, it is found that the radiation ability of a VLF electric dipole in an anisotropic plasma will increase with the operating frequency.