Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

Numerical modeling o f the Alaska 1964 earthquake ionospheric precursors obtained with use o f irregularity in electric potential, which equals 30 kV. Also the positive disturbances in TEC in near-epicenter and magneto-conjugated areas are visible. These positive disturbances in foF2 and in TEC are formed by disturbances of eastward electric field in near-epicenter area. Negative disturbances are formed on both sides from area of positive disturbances by the westward electric field. Meridional component of the electric field leads to the drift in a longitudinal direction o f irregularity in the electron concentration, formed under the action o f zonal electric field component. Fig. 3 presents the calculation results and experimental data from Allouette-1 of latitudinal distributions in foF2 in the longitude o f earthquake epicenter. It is visible a good agreement of calculation results with experimental data. It is possible to note that in both latitudinal profiles the increase in foF2 exists in near-epicenter area. Let consider the effects of additional sources of seismogenic origin on the global distribution of zonal current in the ionosphere (Fig. 4). It is visible the increase of eastward auroral and equatorial electrojets near the longitude of earthquake epicenter. It is possible to note the grater effect in zonal current for the case of irregularity in electric potential, which equals 30 kV. Conclusion Earlier by means of numerical experiments it has been confirmed, that local disturbance in zonal electric fields (Namgaladze et a l, 2009; Klimenko and Klimenko, 2009) or small-scale IGWs (Klimenko and Klimenko, 2009) allows to reproduce the morphology o f ionospheric perturbations observed prior to strong earthquakes. At the analysis o f these numerical results, the generation mechanisms of such zonal electric fields and IGWs were not discussed. In this study we used the numerical experiments with the setting of conditions o f vertical electric field penetration into the ionosphere above earthquake epicenter area. The simulations were carried out with use of the model GSM TIP. It is shown, that the effects o f this seismogenic source in foF2 in near-epicenter area are very similar with Integrated Zonal Current Density, A k m 1 24:00 UT Fig. 3. Top - comparison of latitudinal distributions of foF2 for two neighboring orbits o f the Alouette-1 satellite on March 27, 1964: curve 1 А X = -20°, At = -30.5 h; and curve 2 AX = +5.5°, At = -29 h. An arrow shows the earthquake latitude. Bottom - calculation results. Thin and thick lines - with penetrated vertical electric field at electric potential irregularity, which equals 10 and 30 kV, respectively. a) b) О 60 BO 120 160 180 210 240 270 300 330 360 Geomagnetic Longitude Integrated Zonal Current Density, A km-1 24:00 UT c) Fig. 4. Calculated global maps of integrated zonal current density obtained: a) without seismogenic sources; b) and c) with penetrated vertical electric field at electric potential irregularity, which equals 10 and 30 kV, respectively. Isolines step is 10 A/km. Dashed lines - negative values, solid lines - positive values, dotted lines - zero values. Asterisk - earthquake epicenter position. observational data prior to Alaska earthquake. So it is shown that the penetration o f vertical electric field from lithosphere into the ionosphere can reproduce the ionospheric disturbances observed prior to the strong high-latitude Alaska earthquake. There is a question on opportunity o f penetration o f a vertical electric field from Earth surface into the ionosphere. References Chmyrev V .M , Isaev N .V , Bilichenko S.V , Stanev G.A. Observation by space-borne detectors of electric fields and hydromagnetic waves in the ionosphere over on earthquake center. Phys. Earth and Planet. Inter, 1989, Vol. 57, 110-114. Davies K , Baker D.M. Ionospheric effects observed around the time of the Alaskan earthquake of March 28, 1964. J. Geophys. R es, 1965, Vol. 70, No. 9, 2251-2253. 115