Induced heating effects in an irregular ionosphere

It is possible to observe and control to a limited extent the changes in characteristic ionospheric parameters such as temperature and density by sending high power, high frequency radio waves into the ionosphere and studying the subsequent effects through incoherent scatter techniques. The high frequency wave deposits energy in the ionosphere through absorption and acceleration of the free electrons; the subsequent collisions of the electrons with ions and neutrals; and Landau damping. Focusing and defocusing of the HP rays may arise because of the existence of two or three dimensional gradients in density in the ionosphere. There can be and are, therefore, two and three dimensional irregularities in the electron density distribution causing local alterations in the index of refraction and, consequently, local deviation of the ray paths of the wave in the vicinity of the perturbation. Relative hot or cold temperature spots should result. These density irregularities may be either natural or induced by the presence of the incident radio wave. It is the purpose of this work to look, in two dimensions, at this focusing effect and to estimate the expected electron temperature changes resulting from it by comparison to calculated changes in a horizontally stratified ionosphere. Calculated temperature changes for two kilometer height intervals with and without density perturbations are found to be from 5% to 25% greater than previously calculated results. However, in order to compare the calculated results of this work with measured temperatures, the calculated changes must be averaged over the height resolution of the radar. Excellent agreement is found between the two when this is done