A comprehensive and unique account of the creation of artificially ionized layers in the middle and upper atmosphere, using powerful radio waves. Major physical mechanisms associated with the formation of the ionized region are studied in detail. The main part of the author''s research is devoted to problems associated with the breakdown mechanisms for radio frequency discharges in air. A special chapter deals with breakdown in intersecting pulsed beams and the effects of recombination, diffusion and atmospheric winds on the stability of the structure. The kinetics of the plasma produced are also described. The authors examine possibilities of inducing changes in the chemical composition of the upper atmosphere by means of radio frequence heating, with promising effects on the concentration of constituents such as ozone. The feasibility of using this phenomenon for; ozone healing - in connection with the ozone holes in the polar regions is investigated. The text is a timely treatment of key topics in the field of ionospheric modification.