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.

M.I. Karpov and A.A. Namgaladze quite huge. However, the values don’t exceed the estimations by ( Sorokin et al. , 2007) and measurement results by (.Freund et al., 2009), but lay in the values range of the electric current density associated with thunderstorm activity (.Blakeslee et al., 1989, Krider and Musser, 1982; Le Mouel et al., 2010). Since some authors demonstrate skepticism about the anomaly high values of the seismogenic electric current ( Harrison et al., 2010; Denisensko et a l, 2013], direct measurements of the electric current density over forthcoming earthquake region are highly necessary. In this we compare TEC disturbances observed before two strong earthquakes occurred in Haiti (January 12, 2010) and Japan (March 11, 2011) at different seasons to reveal common features and differences; we also have performed numerical model calculations of the ionospheric effects for corresponding conditions. Observational data results According to the US Geological Survey data, the earthquake with the magnitude M 7.0, the focal depth £>=13 km took place at 16:53 LT on January 12, 2010 at the geomagnetic coordinates of epicenter 35.08 N and 10.29 W. The global 2-hour GPS TEC maps in IONEX format ( Dow et al., 2009) were used to calculate the TEC disturbances relative to the quiet background values, which were obtained as a running average for seven days before the day to be studied. The positive 50 % TEC disturbances were discovered for night-time periods on January 9-12 approximately over the epicenter area and the point magnetically conjugated to epicenter with slight shift to the east (fig. 1). The anomalies in the magnetically conjugated area were stronger and occupied bigger area. Weaker negative deviations were registered at the areas to the west from epicenter meridian. Due to the quiet geomagnetic conditions on January 1-12 and revealed characteristics, observed anomalies were considered as typical ionospheric earthquake precursors (Namgaladze et al., 2013). The Great Tohoku earthquake (M 9.0, D = 30 km) at 14:46 LT on March 11, 2011 was registered at the geomagnetic coordinates of 34.92 N and 144.44 W. Four more earthquakes with the magnitude M > 5 occurred within seven days at the distance of several thousand kilometers from epicenter o f the main event, i.e. inside the typical manifestation zone of ionospheric precursors, so it was not possible to attribute anomalies for specific event. The analysis of the TEC effects was also attended with great difficulties due to non-stable geomagnetic conditions for the considered period. The TEC analysis showed formation of the strongest and stable positive disturbances with the magnitude of 60 % and more at night on March 8 , which were located over the areas to the south from epicenter and to the north from magnetically conjugated point (fig. 2 ) with shift to the east from the epicenter meridian as in the previous case, but anomalies were more symmetrical relative to the geomagnetic equator. Disturbances moving from high to low latitudes were registered on March 10, but were attributed to the geomagnetic storm had taken place that day (Namgaladze et al., 2013). -60 -30 0 30 60 • ш !i ■o3 60' '+-> J2 30' о O' о С -3 0 ' DO £ -6 0 ' -30* O' 30’ -30" 0 ‘ 30' -30" O' 30* M agnetic longitude 180“ -90° 180“ -90“ 180" -90“ Magnetic longitude Fig. 1 GPS observed TEC disturbances (%) for January 9, 2010 (Haiti). Star denotes epicenter location, diamond - magnetically conjugated point, black line - terminator. Numerical calculations and discussion Three-dimensional global first-principle model of the Earth’s upper atmosphere (UAM) was used to simulate ionospheric effects for the considered events. The model calculates temperatures, velocities and densities o f the main neutral and charged components of the near-Earth environment within range from 60-80 km (lower boundary varies depending on task) to the geocentric distance of 15 Earth radii as well as distribution of the electric potential and electric field intensity by solving momentum, heat balance and continuity equations and equation for the electric potential (Namgaladze et al., 1988, 1998). Sources of the external electric current flowing to the Earth were used as an additional (to magnetospheric field-aligned electric currents) model input at the lower boundary in the electric Fig. 2 The TEC disturbances (%) observed on March 8 , 2011 (Japan). 148