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.

*P hysics o f Auroral Phenom ena", Proc. XXXIII A n n u a l Sem inar, A patity, pp . 171 -1 7 3 , 2011 © Kola Science Centre, Russian Academy of Science, 2011 Polar Geophysical Institute ON THE CONNECT ION BETW EEN VAR IAT ION S OF ATMOSPHER IC ELECTRIC FIELD A S M EA SURED AT G ROUND SURFACE IN THE CENTRAL ANTARCT ICA A N D IONOSPHER IC POTENT IAL A.A. Kruglov A.V, Frank-Kamenetsky G. B um s2, J. F ren ch2’V.N. M o rozov3 1. Arctic and Antarctic Research Institute, Saint - Petersburg, Russia; 2. Australian Antarctic Division, Kingston, Australia 3. Main Geophysical Observatory, Saint - Petersburg, Russia Abstract. The solar wind generator contributes in a variable manner to the ionosphere-to-ground potential difference at sites in the Polar Regions. It averages -20% of the contribution of the meteorological batteries at such sites. At times of strong solar wind interaction, much larger contributions to the atmospheric circuit in Polar Regions can occur. Regular measurements of the variations of atmospheric electric fields performed at Vostok Station (ф = 78.45° S; X = 106.87° E, elevation 3500 m) in Antarctica are compared with the value of solar-wind-imposed ionospheric electric potential above the station (O i) derived from a Weimer model. Observed positive correlation of AEz with <J>i affirms the truth of this statement. Introduction At high latitudes, the interaction of the solar wind and the Earth’s magnetic field imposes on the geoelectric field a variable dawn-to-dusk potential drop of between 20 and 150 kV. Large-scale (>200 km) horizontal electric fields in the ionosphere map into the vertical component of the electric field near the Earth’s surface (Park, 1976b, Hays P.B., Roble, R.G., 1979). Frank-Kamenetsky et al., (2001) show that the geoelectric field at Vostok is modulated by the By and Bz components of the interplanetary magnetic field (IMF). Tinsley et al. (1998) compared variations of the surface electric field, AEz (the observed electric field at South Pole minus the Carnegie curve scaled to the average o f Ez) with variations in the calculated overhead ionospheric electric potential inferred using the Hairston-Heelis model, (Hairston and Heelis, 1990). The authors found positive correlations. Comey et al. (2003) and Bums et al. (2005) shows linear correlation between the variations of Weimer- model (Weimer, 1995) calculated potential above Vostok and variations o f near-ground vertical electric field for each hour over bi-monthly intervals, thus demonstrating that Antarctic polar plateau geoelectric field measurements can be used to investigate polar convection. In this paper we will study the correlations between the electric field variations near the ground measured at Vostok station, Antarctica (geog 78.466S, 106.838E; mag 83.68S, 54.92E) and Weimer -model (Weimer, 2001) ionospheric potential for 1998-2001. Analytical m odel We believe that electric potential in the polar ionosphere can be presented as a sum of external (the solar-wind-imposed potential <X>Sw) and internal (thunderstorm imposed potential Ф0) parts. Similarly, surface electric field can be considered as the sum o f the solar-wind-imposed field (ESw) and thunderstorm field (ETH). In order to find the solar-wind- imposed field (Esw) part of the total electric field measured near the earth surface (Ez) we need to subtract the thunderstorm part (ETH) from the measured field. E sw _ E z - E th (1) For this purpose we solved the problem of downward mapping of the ionospheric field. The equation for electric potential can be written in a spherical coordinates as: r2 dr dr г2ътвдв дв г2sin26 ( 2 ) Where A (r) = Я0е а , Лд - the electric conductivity near the earth surface (Atmosfera. Handbook, 1992), R - Earth radius. Boundary conditions for solving the equations (2) are the following: p U = o <P\„ = <P(r- where r r the altitude of the ionosphere and 8 8 ^ Д ф )= р ^ (О О В в )+ ^ £ Ц CO Sy^+4siny$/f(C056?) ' > r=0 r=J j =1 The equation (3) we take from Weimer model (Weimer 1995, 2001). The solution of equation (2) is sought in the form o f an expansion in spherical harmonics (Jackson, 1962) <p(r, e,<t>) = Y J Y 4 <pjj ( r ) -Yv ( 0 , 4 ) , i=0 j=-i <р^(г) = ^dCl(p(r, в ,ф)Уу(0,<j>),d£l = sin ddddtf) (4). Using this expansion, we obtain for <Py ( r ) the equation: r d r r dr /u = i(i + \),i = 0,1,2., (5) If r » R , a » — the solution of equation (5) r with boundary conditions (3) can be written as following: 171