Ionospheric modification by high power radio waves

Investigations using powerful, high frequency (HF) radio waves to temporarily modify the ionosphere are reviewed. Studies of the natural upper atmosphere have been conducted using these controlled, active experiments by observing the ionospheric response to HF induced perturbations. Other basic physics investigations have examined the ionosphere and its properties and behavior as a plasma. Topics examined include ionospheric heating, parametric plasma instabilities, large-scale field-aligned ionospheric density irregularities, short-scale striations, and additional nonlinear effects. It is concluded that HF ionospheric modification research continues to have important applications in the fields of aeronomy, space physics, plasma physics, and telecommunications science.