Near Field Generated by a VLF Magnetic Dipole With Arbitrary Orientation in an Anisotropic Magnetoplasma

With the increasing importance of space-borne antennas in very low-frequency (VLF: 3–30 kHz) transmitting system, it is essential to study radiation characteristics of a radiator in ionosphere. In this article, with an environment of anisotropic magnetoplasma, the near field of a magnetic dipole is treated. Since two eigenmodes coexist in an anisotropic scenario, i.e., ordinary wave (O-wave) and extraordinary wave (E-wave) with different attenuations, a semi-analytical method is proposed to accurately investigate the near field in an anisotropic plasma. Calculations and analysis show that the primary contribution to the field generated by a magnetic dipole with arbitrary orientation comes from the source projection parallel to the geomagnetic field. The results show that the O-wave maintains an amplitude comparable to that of the E-wave in the near zone. Moreover, the radiation pattern shows that the amplitude of E-waves becomes weaker with increasing tilt angle, while the amplitude of O-waves is not sensitive to the change of the geomagnetic tilt angle.