Physics of auroral phenomena : proceedings of the 37th Annual seminar, Apatity, 25 - 28 February, 2014 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Изд-во Кольского научного центра РАН, 2014. - 125 с. : ил., табл.

Simulation study o fthe disturbance o f the spatial structure o f the daytime high-latitude ionosphere by powerful HF radio waves decreases due to elastic and inelastic collisions between electrons and other particles of ionospheric plasma, and a period of recovery comes. Figure 2. Simulated distributions of the electron Figure 3 . simulated distributions of the electron concentration (in units of 10 m ) at level of concentration (in units of 1011m"3) in the magnetic meridian 280 km obtained under natural conditions plane, lying across the ionospheric heater, obtained under without artificial heating (top panel) and natural conditions without artificial heating (top panel) and obtained on condition that the ionospheric heater obtained on condition that the ionospheric heater has been has been operated during the period of operated during the period of approximately seven minutes approximately seven minutes (bottom panel). (bottom panel). The location of the heater is indicated by The electron concentration cavity, created die black pointer at the bottom panel, artificially, is indicated by black pointer at the bottom panel. In the model calculations, it was assumed that the ionospheric heater provides a beam width of 14.5° (such as the beam width of the ionospheric high-frequency heating facility near Tromso, Scandinavia). Therefore, the diameter of the illuminated region is approximately 88 km at 300 km altitude. As a consequence of the convection of the ionospheric plasma at F-layer altitudes, the volume of plasma, disturbed by a powerful HF wave, can abandon the region illuminated by an ionospheric heater. Therefore, the horizontal section of disturbed region at F-layer altitudes can differ from the horizontal section of the region illuminated by the heater. Let us consider the simulated spatial distributions of the ionospheric parameters. These distributions are presented in Figs. 2 and 3. The simulation results, obtained under natural conditions without artificial heating, contain various large-scale inhomogeneous structures characteristic for the high-latitude ionosphere. The electron concentration distributions contain the well-known tongue of ionization, extended from the local noon side of the Earth across the polar cap to the night side, as well as the main ionospheric trough on the night side of the Earth (Fig-2). The simulation results, obtained on condition that the ionospheric heater has been operated during the period of 435 seconds, indicate that the electron concentration cavity is formed on the day side in the vicinity of the location 88