SIMULATION STUDY OF THE DISTURBANCE OF THE SPATIAL STRUCTURE OF THE DAYTIME HIGH-LATITUDE IONOSPHERE BY POWERFUL HF RADIO WAVES G.I. Mingaleva, V.S. Mingalev (Polar Geophysical Institute, Apatity, Russia, e-mail: mingalev@pgia.ru) Abstract. The large-scale spatial structure of the daytime high-latitude F-region ionosphere, disturbed by powerful high-frequency radio waves, is studied with the help of the numerical simulation. It is known that high-power HF radio waves, pumped into the ionosphere, can cause the disturbance of the spatial structure of the F-region ionosphere. In this study, the mathematical model of the high-latitude ionosphere, which can be affected by powerful high-frequency radio waves, is utilized to study the dimension of the area covered by the disturbance in the horizontal plane. The distributions of the ionospheric parameters were calculated on condition that an ionospheric heater, situated at the point with geographic coordinates of the HF heating facility near Tromso, Scandinavia, has been operated, with the ionospheric heater being located on the day side of the Earth. Introduction Experimental data indicate that high-power high-frequency radio waves, pumped into the ionosphere, can cause a variety of physical processes in the ionospheric plasma. Some of such processes can result in the disturbances of the height profiles of the ionospheric parameters at F-layer altitudes (above approximately 150 km). It is known that powerful HF waves can produce significant large-scale variations in the electron temperatures and densities at F- layer altitudes [Gordon and Carlson, 1974; Mantas et al., 1981; Duncan et all., 1988; Gustavsson et al., 2001; Pedersen et al., 2008]. Mathematical models may be applied for the investigation of the response o f the F region to a powerful HF wave. However, to date very few mathematical models of the high-latitude F region, which can be affected by a powerful HF wave, have been developed. In the Polar Geophysical Institute (PGI), one of such mathematical models has been developed [Mingaleva and Mingalev, 1997]. This model has been used to simulate the influence of the HF waves on the expected response of the ionospheric parameters at F-layer altitudes to HF heating [Mingaleva and Mingalev, 2013 and references therein]. The purpose of the present paper is to examine how high-power high-frequency radio waves, pumped into the high-latitude ionosphere, influence on the ionospheric parameters distributions in the horizontal directions at F-layer altitudes. The distributions of the ionospheric parameters were calculated on condition that an ionospheric heater, situated at the point with geographic coordinates of the HF heating facility near Tromso, Scandinavia, has been operated, with the ionospheric heater being located on the day side of the Earth on the magnetic meridian of 15.00 MLT. The mathematical model of the high-latitude ionosphere, which can be affected by powerful high-frequency radio waves, developed earlier in the PGI, is utilized in this study. Numerical model The mathematical model of the high-latitude ionosphere, utilized in this study, produces three-dimensional distributions of the electron density, positive ion velocity, and ion and electron temperatures. It encompasses the ionosphere above 36° magnetic latitude and at distances between 100 and 700 km from the Earth along the magnetic field line for one complete day. The applied model takes into consideration the strong magnetization of the plasma at F-layer altitudes and the attachment of the charged particles of the F-region ionosphere to the magnetic field lines. As a consequence, the F-layer ionosphere plasma drift in the direction perpendicular to the magnetic field В is strongly affected by the electric field E and follows ExB convection paths (or the flow trajectories). In the model calculations, a part of the magnetic field tube of the ionospheric plasma is considered at distances between 100-700 km from the Earth along the magnetic field line. The temporal history is traced o f the ionospheric plasma included in this part of the magnetic field tube moving along the flow trajectory through a neutral atmosphere. By tracing many field tubes of plasma along a set of flow trajectories, we can construct three-dimensional distributions of ionospheric quantities. As a consequence of the strong magnetization of plasma at F-layer altitudes, its motion may be separated into two flows: the first, plasma flow, parallel to the magnetic field; the second, plasma drift in the direction perpendicular to the magnetic field. The parallel plasma flow in the considered part o f the magnetic field tube is described by the system of transport equations, which consists of the continuity equation, the equation of motion for ion gas, and heat conduction equations for ion and electron gases. The equations provide for the direct and resonantly scattered EUV solar radiation, energy-dependent chemical reactions, frictional force between ions and neutrals, accelerational and viscous forces of ion gas, thermal conductions o f electron and ion gases, heating due to “Physics o f Auroral Phenomena”, Proc. XXXVII Annual Seminar, Apatity, pp. 86-89, 2014 © Kola Science Centre, Russian Academy of Science, 2014 Polar Geophysical Institute 86

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