TEMPORAL BEHAVIOR OF ARTIFICIAL SMALL-SCALE IONOSPHERIC IRREGULARITIES - REVIEW OF EXPERIMENTAL RESULTS

Features of artificial small-scale ionospheric irregularities (ASI) in duced at F-region heights by powerful HF waves are discussed. The inve stigations presented here were performed during the past two decades a t the Zimenki and Sura heating facilities, located at middle latitudes near Nizhniy Novgorod, Russia, as well as at the Gissar facility loca ted at a lower latitude near Dushanbe, Tadzhikistan. The measurements were made by a variety of diagnostic methods employing artificial fiel d-aligned scattering of HF and VHF radio waves, sounding of the distur bed region by means of low-power probing waves and testing of the arti ficial turbulence by means of stimulated electromagnetic emission (SEE ). The dependence of ASI on such parameters as transverse scale length of the artificial irregularities, their location in the disturbed reg ion, the power of the heating wave, the duration of HF radiation, geop hysical conditions, aftereffects of the preceding modification, and th e schedule of hearer operation is considered for both the development stage after pump turn-on and the decay stage after pump turnoff. The t emporal evolution of ASI spectral characteristics during the heater pe riod is discussed. An empirical model for the ASI, based on the data a vailable, was elaborated and verified by computer simulation of SEE ge neration. (C) 1997 Elsevier Science Ltd.