Investigation by backscatter radar of artificial irregularities produced in ionospheric plasma heating experiments

The artificial ionospheric turbulence occurs in the ionosphere illuminated by high power HF radio waves. There are a lot of irregularities stretched along the geomagnetic field in this region. The investigation of the artificially disturbed ionospheric region is based on the reception of back scattered signals (BSS) which permits the basic parameters of this region to be estimated and its inhomogeneous structure to be described. Experiments were carried out using 'Sura' heating facility in the frequency range of f = 4.7 - 9 MHz (ordinary mode) with the effective radiated power P-eff = 50-70 MW beamed vertically upwards. The most important dynamic and statistical BSS characteristics (the built-up time, the relaxation and autocorrelation times, the BSS amplitude spatial correlation function and power spectra) were measured using probe waves in the frequency range of f(p) = 1.68-6 MHz that made it possible to obtain the basic parameters of the artificial irregularities. The model representation of a disturbed region in a form of a periodic structure gives a possibility to evaluate the scale of the structure, the whole size of the disturbance and its power and to calculate the main BSS characteristics. (C) 1997 Elsevier Science Ltd.