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 F.S. Mingalev ion-neutral friction, Joule heating, heating due to solar EUV photons, heating caused by the action of the powerful HF radio waves, and electron energy losses due to elastic and inelastic collisions. The applied mathematical model takes into account the heating mechanism, caused by the action of the powerful HF radio waves and connected with the formation of short-scale field-aligned plasma irregularities in the electron hybrid resonance region. These irregularities are responsible for the anomalous absorption of the electromagnetic heating wave passing through the instability region and cause anomalous heating of the plasma. The rate of this anomalous heating is taken from the study by Blaunshtein et al. [1992]. In the present study, the electric field distribution, which is the combination of the pattern В of the empirical models of high-latitude electric fields of Heppner [1977] and the empirical model of ionospheric electric fields at middle latitudes, developed by Richmond el al. [1980], is utilized. The utilized electric field distribution is a steady non-substorm convection model. Using this convection model, we calculate the plasma drift velocity along the convection trajectories, which intersect the F-layer volume illuminated by an ionospheric heater situated at the point with geographic coordinates o f the HF heating facility near Tromso, Scandinavia. For these convection trajectories, we obtain variations of profiles against distance from the Earth along the geomagnetic field line of the ionospheric quantities with time (along the trajectory) by solving the system of transport equations. These profiles may be used for the construction of two-dimensional distributions of ionospheric quantities along the each flow trajectory. By taking a set of flow trajectories and 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. In this study, the spatial configuration of 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]. The numerical method, boundary conditions, neutral atmosphere composition, thermospheric wind pattern, and input parameters of the model were in detail described in the studies by Mingaleva and Mingalev [1996, 1997, and 1998]. Simulation results Different combinations of the solar cycle, geomagnetic activity level, and season may be described by the utilized mathematical model. In the present study, the calculations are performed for autumn (5 November) and not high solar activity conditions (F 10.7 =110) under low geomagnetic activity (Kp=0). In the present study, the calculations were made for two distinct cases. For the first case, we simulated the distributions of the ionospheric parameters under natural conditions without a powerful high- frequency wave effect. For the second case, 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. For the second case, firstly, we made a series of calculations to choose the wave frequency which provides the maximal effect of 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, /ф [Mingaleva and Mingalev, 2013]. It was found that this most effective frequency is 4.9 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 of the f eg 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 f435 seconds. The results of simulations are partly presented in Figs. 1-3. Simulation results 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 visible decrease in the electron concentration profile at the levels near to the F2-layer peak (Fig. 1). In particular, the powerful HF waves lead to the decrease of 24% in electron concentration at the level o f the F2-layer peak. After turning off of the heater, the electron temperature Figure 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 435 seconds after turn on (marked by the symbol *). 87