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.

G.I. Mingaleva and V.S. Mingalev of the ionospheric heater (Figs. 2 and 3). Inside this cavity, powerful HF waves lead to a decrease of about 20% in the electron concentration at the level of the F2-layer peak. The simulation results indicate that the cross sections of the artificial electron concentration cavity have dimensions of about 100-150 km in the horizontal directions at the levels of the F layer (Figs. 2 and 3). These dimensions do not coincide with the horizontal section of the region, illuminated by the heater, due to the convection of the ionospheric plasma. It is seen that these dimensions are much less than the horizontal sizes of the natural large-scale inhomogeneous structures characteristic for the high-latitude ionosphere, in particular, of the main ionospheric trough. The dimension of the artificial electron concentration cavity in the direction of the magnetic field line is about some hundreds of kilometers (Fig. 3). Conclusion To calculate three-dimensional distributions of ionospheric parameters in the high-latitude F layer, modified by the action of the ionospheric high-frequency heating facility, situated at the point with geographic coordinates of the HF heating facility near Tromso, Scandinavia, the mathematical model of the high-latitude ionosphere, developed earlier in the PGI, was utilized. Firstly, we simulated the distributions of the ionospheric parameters under natural conditions without a powerful high-frequency wave effect. Secondly, the distributions of the ionospheric parameters were calculated on condition that the ionospheric heater has been operated during the period of 435 seconds, using the most effective frequency for the large-scale F2-layer modification, with the heater being located on the day side of the Earth on the magnetic meridian of 15.00 MLT. In the second case, powerful HF waves lead to a decrease of about 20% in the electron concentration at the level of the F2-layer peak over the ionospheric heater. The cross sections of the artificial electron concentration cavity have dimensions of about 100-150 km in the horizontal directions at the levels of the F layer. This cavity is stretched in the direction of the magnetic field line for some hundreds of kilometers. Acknow ledgem ents. This work was partly supported by Grant No. 13-01-00063 from the Russian Foundation for Basic Research. References Blaunshtein, N.Sh., Vas’kov, V.V., Dimant, Ya.S. Resonance heating of the F region by a powerful radio wave. Geomagnetism and Aeronomy, 32(2), 95-99, 1992 (Russian issue). Duncan, L.M., Sheerin, J.P., Behnke, R.A. Observations of ionospheric cavities generated by high-power radio waves. Physical Review Letters, 61, 239-242, 1988. Gordon, W.E., Carlson, H.C. Arecibo heating experiments. Radio Science, 9, 1041-1047, 1974. Gustavsson, B., Sergienko, Т., Rietveld, M.T., Honary, F., Steen, A., Brandstrom, B.U.E., Leyser, T.B., Aruliah, A.L., Aso, Т., Ejiri, М., Marple, S. First tomographic estimate of volume distribution of HF-pump enhanced airglow emission. Journal of Geophysical Research, 106, 29105-29124, 2001. Hardy, D.A., Gussenhoven, M.S., Brautigam, D. A statistical model of auroral ion precipitation. Journal of Geophysical Research, 94, 370-392, 1989. Heppner, J.P. Empirical models of high-latitude electric fields. Journal of Geophysical Research, 82, 1115- 1125, 1977. Mantas, G.P., Carlson, H.C., La Hoz, C.H. Thermal response of F-region ionosphere in artificial modification experiments by HF radio waves. Journal of Geophysical Research, 86, 561-574, 1981. Mingaleva, G.I., Mingalev, V.S. The formation of electron temperature hot spots in the main ionospheric trough by the internal processes. Annales Geophysicae, 14, 816-825, 1996. Mingaleva, G.I., Mingalev, V.S. Response of the convecting high-latitude F layer to a powerful HF wave. Annales Geophysicae, 15, 1291-1300, 1997. Mingaleva, G.I., Mingalev, V.S. Three-dimensional mathematical model of the polar and subauroral ionosphere, pp. 251-265, in Modeling of the upper polar atmosphere processes, eds. V.E. Ivanov, Ya.A. Sakharov, and N.V. Golubtsova, PGI, Murmansk, 1998, (in Russian). Mingaleva, G.I., Mingalev, V.S. Simulation study of the modification of the high-latitude ionosphere by powerful high-frequency radio waves. Journal of Computations & Modelling, 3(4), 287-309,2013. Pedersen, Т., Esposito, R., Kendall, E., Sentman, D., Kosch, М., Mishin, E., Marshall, R. Observations of artificial and natural opticafemissions at the HAARP facility. Annales Geophysicae, 26, 1089-1099,2008. Richmond, A.D., Blanc, М., Emery, B.A., Wand, R.H., Fejer, B.G., Woodman, R.F., Ganguly, S., Amayenc, P., Behnke R.A., Calderon, C., Evans, J.V. An empirical model of quiet-day ionospheric electric fields at middle and low latitudes. Journal of Geophysical Research, 85, 4658-4664, 1980. 89