VLF-ELF radiation characteristics of a 90°-phased crossed-dipole array in a cold multicomponent magnetoplasma

Abstract

Linear electromagnetic theory is used to find the VLF‐ELF radiation characteristics of a quadrature‐phased crossed‐dipole array in a cold multicomponent magnetoplasma. Each dipole is perpendicular to the static magnetic field B0, and the current on each is assumed to have a skin‐triangular distribution. Formal solutions valid throughout the VLF and ELF ranges are derived for the total radiated complex power and mutual coupling power. These solutions are used to obtain both numerical results and approximate closed‐form expressions for mutual input impedance ΔZ applicable to the driving terminals of either dipole of the array. Approximate closed‐form expressions for the power fluxes parallel and perpendicular to B0 are also derived. When a right‐circularly phased dipole array is used as a radiating source in the VLF range, the total power radiated into the whistler mode is increased, and the power flux along the field line is enhanced by a factor of 4 compared to that from a single dipole carrying the same current. In the ELF range, the effects are similar but more complicated. The mutual input reactance due to the effects of medium anisotropy and circular phasing of the dipole array are found to be negligible. It is shown that the power flux along B0 from a right‐circularly phased dipole array peaks by at least 1 order of magnitude at approximately half the electron gyrofrequency. This result suggests a possible use of the proposed array as a radiating source to trigger artificially stimulated VLF emissions.

Radiation From a Multiple Dipole Antenna With Phased Excitation in a Magnetoplasma

“…Substituting this relationship into (21), we can introduce the total radiation resistance R Σ = 2P Σ /|I 0 | 2 and the partial radiation resistances R m = 2P m /|I 0 | 2 of the multiple dipole antenna. In the case of a single dipole where K = 1 and Φ m = 1, these radiation resistances will be denoted as R , where δ m,n is the Kronecker delta.…”

“…In the case of a single dipole where K = 1 and Φ m = 1, these radiation resistances will be denoted as R , where δ m,n is the Kronecker delta. Then, from (21), the total radiation resistance is derived in the form…”

“…The simplicity of realization of antenna systems on the basis of electric dipoles makes them attractive in comparison with other types of antennas. Despite the recent upsurge of interest in the characteristics of electric dipole antennas and their arrays in a magnetoplasma [15], [16], [17], [18], [19], [20], only one theoretical work [21] has been published to date on the radiation characteristics of a phased electric-dipole array capable of exciting twisted waves under ionospheric conditions, as far as we are aware. The analysis in [21] is primarily focused on the input impedance of a turnstile antenna in the form of two orthogonal electric dipoles with quadrature-phased currents in the VLF band.…”

“…Despite the recent upsurge of interest in the characteristics of electric dipole antennas and their arrays in a magnetoplasma [15], [16], [17], [18], [19], [20], only one theoretical work [21] has been published to date on the radiation characteristics of a phased electric-dipole array capable of exciting twisted waves under ionospheric conditions, as far as we are aware. The analysis in [21] is primarily focused on the input impedance of a turnstile antenna in the form of two orthogonal electric dipoles with quadrature-phased currents in the VLF band. However, the efficiency of excitation of different azimuthal field harmonics by such an antenna was not considered in [21].…”

“…The analysis in [21] is primarily focused on the input impedance of a turnstile antenna in the form of two orthogonal electric dipoles with quadrature-phased currents in the VLF band. However, the efficiency of excitation of different azimuthal field harmonics by such an antenna was not considered in [21].…”