Physics of auroral phenomena : proceedings of the 36th Annual seminar, Apatity, 26 February – 01 March, 2013 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2013. - 215 с. : ил., табл.

G.I. Mingaleva and V.S. Mingalev anomalous heating of the plasma. The rate of this anomalous heating is included in the heat conduction equation for electron gas. The concrete expression to the rate of anomalous heating was taken from the study by Blaunshtein et al. [1992]. Using the given electric field distribution, we calculate the plasma drift velocity along the convection trajectories, which intersect the F-layer volume illuminated by HF heating facility near Tromso, Scandinavia. For these convection trajectories, we obtain variations o f profiles against distance from the Earth along the geomagnetic field line of the ionospheric quantities with time (along the trajectory) by solving the system o f transport equations described above. These profiles result in two-dimensional distributions o f ionospheric quantities along the each flow trajectory. Using these two-dimensional distributions along the each convection trajectory, we can construct three- dimensional distributions of ionospheric quantities, modified by the action of the ionospheric heater. S im u la tio n resu lts The utilized mathematical model can describe different combinations of the solar cycle, geomagnetic activity level, and season. In the present study, the calculations are performed for autumn (5 November) and not high solar activity conditions (F10. 7 = l 10) under low geomagnetic activity (Kp=0). The spatial configuration o f the electron and proton precipitation zones as well as intensities and average energies of the precipitating electrons and protons were chosen as consistent with the statistical model of Hardy et al. [1989]. 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, we made calculations for two distinct cases. For the first case, we obtained the distributions of the ionospheric parameters under natural conditions without a powerful high-frequency wave effect. For the second case, the distributions o f the ionospheric parameters were obtained on condition that the ionospheric high-frequency heating facility near Tromso, Scandinavia has been operated. For the second case, firstly, we made a series of calculations to choose the wave frequency which provides the maximal effect o f HF heating on the electron concentration at the levels near to the F2-layer peak, that is, the most effective frequency for the large-scale F2-layer modification,^-, [Mingaleva and Mingalev, 2003]. It was found that this most effective frequency is 2.6 MHz on condition that the maximal value of the effective absorbed power (EAP) is equal to 30 MW which is quite attainable for the heating facility near Tromso. Secondly, calculations were carried out, using the pointed out values o f the f eff and EAP, to study how the HF radio waves affect the large-scale high-latitude F-layer modification. The ionospheric heater was supposed to operate during the period o f five minutes, with the heater being located on the night side o f the Earth on the magnetic meridian of 01.20 MLT. The results o f simulations are partly presented in Figs. 1-3. Results o f simulation indicate that a great energy input from the powerful HF wave arises at the level, where the wave frequency is close to the frequency of the electron hybrid resonance, when the ionospheric heater is turned on and operates. At this level, pronounced peak arises in the electron temperature profile. At this peak, the electron temperature can increase for some thousands of degrees. The increase in the electron temperature results in a rise in the electron gas pressure. From the level where the electron Fig. 1 Profiles of the electron concentration versus distance from the Earth along the geomagnetic field line, situated in the illuminated region, obtained under natural conditions without artificial heating (marked by the symbol о ) and disturbed by the heater at the moment of approximately four minutes after turn on (marked by the symbol *). gas pressure peak is located, the upward and downward electron gas fluxes arise. Due to the electrical neutrality of the ionospheric plasma, the ion gas begins to move, too. Thus, ionospheric plasma fluxes arise from the level where the maximum energy input from the powerful HF wave takes place. Owing to these fluxes, a visible decrease in the electron concentration profile can arise not only near the level of maximum energy absorption from the powerful HF wave, but also near the F2-layer peak (Fig.l). It is seen that powerful HF waves lead to the decrease of more than 40% in electron concentration at the level o f the F2-layer peak. After turning off of the heater, the electron temperature decreases due to elastic and inelastic collisions between electrons and other particles of ionospheric plasma, and a period o f recovery comes. The simulation results, obtained on condition that the ionospheric heater has been operated during the period of five minutes, indicate that the electron temperature hot spot is formed on the night side in the vicinity o f the location 160