The contribution of artificial D-region disturbances to the ionospheric VLF wave environment

Artificial ionospheric disturbances are created by intense high-frequency (HF) radiation from ground-based facilities and very-low-frequency (VLF) radiation from Navy transmitters. We apply Stanford Full-Wave Method (SFWM) to scattering of the VLF waves propagating in the Earth-ionosphere waveguide (EIW) by such ionospheric disturbances, using Born approximation. The waves are scattered both into the EIW (in the forward direction) and into the ionosphere (both forward and upward into a whistler “column”). In the case of HF heating, the upward-scattered wave intensity may significantly exceed the waveguide leakage into the ionosphere, while for the VLF-heated ionosphere, it is relatively small.