VLF Scattering Characteristics of a Finite Cylindrical Conductor in the Anisotropic Ionosphere

Abstract

Spaceborne antennas operated in the very low frequency (VLF: 3-30kHz) ranges play important roles in ionosphere exploration, satellite communication, and submarine communication. In this paper, we idealize the receiving antenna mounted on the satellite as a finite-length conducting cylinder and establish a theoretical approach for scattering characteristics of a cylinder in the ionosphere, behaving as an anisotropic plasma. Analytical expressions of scattered fields and current distributions of cylinders are derived with the integral equation (IE) method and method of moment (MoM). Contributions from the ordinary wave (O-wave) and extra-ordinary wave (E-wave) are combined to represent the total scattering and surface current induced on the cylinder. Numerical results show that the current distribution exhibits sensitivity to the dimension of the structure, including the radius and length of the cylinder and the incident angle. For instance, a symmetrical current distribution is obtained under normal incidence, while an offset current is generally found under oblique incidence. A “cohesion effect” along the direction of the geomagnetic field in the scattered pattern is observed. Moreover, the scattering to the E-wave is greater than that of the O-wave. Interestingly, the radar cross section (RCS) is gradually suppressed as the observation angle increases, in contrast to the conventional scattering in the free space. Potentially, the theoretical formulations and the predicted phenomena would help in understanding the basic properties of the VLF scattering in the ionosphere and planning related ionospheric experiments.

Keywords

• VLF waves
• finite-length conducting cylinder
• anisotropic ionosphere
• surface current
• RCS