V. Sotnikov, Air Force Research Laboratory; N. Gershenzon, Riverside Research Institute; N. Zechar, Riverside Research Institute; R. Schueler, Riverside Research Institute; T. Kim, Asian Office of Aerospace Research and Development
Keywords: Very Low Frequency (VLF) waves, Ionosphere, Wave turbulence
Abstract:
A novel comprehensive effort that incorporates theory and computer simulations to investigate propagation of high frequency (HF) waves through a region with developed whistler wave turbulence in the ionospheric F-layer is analyzed. This research aims to explore the impact of artificially excited whistler turbulence on propagation properties of HF waves and the possibility to generate sideband emissions with frequency shifts corresponding to frequencies in excited whistler wave spectrum. Mechanism of whistler wave excitation can be parametric interaction of launched from the ground HF waves propagating in the underdense regime in the F layer. In order to analyze HF wave scattering in spatially and time varying ionospheric plasma Finite Difference Time Domain (FDTD) code was developed. This three- and two-dimensional FDTD code allows to model electrodynamics in plasma environments, by discretization of partial differential equations. Important new feature of the code is the ability to take into account not only spatially varying but also time varying turbulent pulsations excited in the ionosphere. Using this FDTD code we will present results on generation of HF sidebands in the process of propagation of HF wave through an ionospheric F layer region containing whistler wave turbulence. Mechanism of sideband generation is the nonlinear coupling of HF and whistler waves. This coupling can be numerically analyzed due to the ability of the code to describe not only spatial but also time varying perturbations in plasma. It is worth mentioning that the effect of sideband generation can be observed only when resonance conditions in frequency and wave vector domains are simultaneously imposed on interacting HF and whistler waves.
Numerical results also confirm that the presence of whistler waves in the absence of resonance produces negligible scattering and do not generate sidebands. Appearance of the HF sidebands generated by the proposed nonlinear mechanism can strongly impact performance of surveillance and communication systems.
Related References:
1. S. Pokhrel, V. Shankar, and J. Simpson, “3-D FDTD Modeling of Electromagnetic Wave
Propagation in Magnetized Plasma Requiring Singular Updates to the Current Density Equation”
IEEE Transactions on Antennas and Propagation, Vol. 66, No. 9, 2018.
2. D. Main and V. Sotnikov, “Parametric interaction between ELF and VLF waves: 3D LSP simulation results”, Phys. Plasmas 27, 022304, 2020.
Approved for public release. Case Number: AFRL-2022-0705
Date of Conference: September 27-20, 2022
Track: Atmospherics/Space Weather