VLF fields of a horizontal dipole below the polar anisotropic ionosphere

A study is made of VLF fields excited by a horizontal dipole in the waveguide formed between the ice-covered ground and the anisotropic ionosphere of Antarctica. Numerical results are presented which describe the excitation, propagation, and polarization of radiated energy for ionospheres typical during both summer (daylight) and winter (night) conditions in Antarctica. The polarization of fields observed at the ice surface is found to be a function of both azimuth and range. Ice layer characteristics have significant effects on received fields, especially those of the quasi-TM type. The possible excitation of a TM-type surface wave at the ice-air interface under special conditions is also discussed. Fields propagating with wave numbers corresponding to quasi-TE modal solutions are least attenuated in the waveguide. Summer ionospheres tend to increase modal attenuation rates. Results are applied to a real experimental situation in Antarctica involving a horizontal dipole source and trans-Antarctic propagation paths.