High powered radio waves directed to the upper atmosphere and ionosphere can produce changes in composition, electron density, optical emissions and other radio waves at various frequencies. The cause of many of these effects is still unknown and just what perturbation will occur for a given power and frequency input is still theoretically unexplained. This project is an experimental investigation of ionospheric modification by modulated high power HF radio waves using the HF heating facility and the incoherent scatter radar facility at the Arecibo Observatory in Puerto Rico. The objectives of these experiments are to study the convective heating and cooling response in the natural F-Region ionosphere, to study electron changes in the electron density in the D and E regions, to analyze for instability dynamic thresholds and to investigate predicted thermal self-focusing instability dependence on magnetic field orientation, pump power, frequency and electron temperature.fz
