Radiation Efficiency of Parametric Antenna in the Ionospheric Plasma

Abstract:

It is well known that only a small portion of radiated power from a very low frequency (VLF) loop antenna is transferred to an electromagnetic part of VLF wave spectrum (whistler modes) with the rest of radiated power lying in a quasi-electrostatic part of the VLF wave spectrum – low oblique resonance oscillations (LOR). In order to increase portion of radiated power going into the electromagnetic part of the wave spectrum concept of a parametric antenna in the ionospheric plasma is analyzed. Such antennas are capable of exciting electromagnetic radiation fields, specifically the creation of whistler waves generated at the VLF range, which are also capable of propagating large distances away from the source region. The mechanism of whistler wave generation is considered a parametric interaction of LOR oscillations excited by conventional loop antenna. The transformation of LOR waves on quasi-neutral density perturbations generated by a dipole antenna operating in the frequency range above an ion cyclotron frequency gives rise to electromagnetic whistler waves on combination frequencies. In this approach extended plasma volume around a loop antenna represents a parametric antenna. Simulation to demonstrate excitation and spatial structure of VLF waves excited by a loop antenna using a PIC code LSP will be presented as well. Possible applications including the wave-particle interactions to mitigate performance anomalies of Low Earth Orbit (LEO) satellites, active space experiments, communication via VLF waves, and modification experiments in the ionosphere will be discussed.