Combined operation of two ground transmitters for enhanced ionospheric heating

The combined operation of an HF or MF ground transmitter and a VLF transmitter for enhanced ionospheric heating is discussed. The HF or MF transmitter, operated in a pulsed mode, can preferentially produce short-scale density striations that can render the nonlinear mode conversion of the subsequently launched VLF waves into lower hybrid waves. In addition to the mode conversion process, the VLF waves, if intense enough, can also excite meter-scale density striations and lower hybrid waves via parametric instabilities. Intensified density striations and enhanced airglow are expected, and they can be detected by incoherent backscatter radars and photometers, respectively. The feasibility and planning of the proposed experiments are addressed. (author)