Physics of auroral phenomena : proceedings of the 38th annual seminar, Apatity, 2-6 march, 2015 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Издательство Кольского научного центра РАН, 2015. - 189 с. : ил., табл.

THE ELECTRIC POTENTIAL DISTRIBUTION IN THE DISTURBED POLAR IONOSPHERE: COMPARISON OF STATISTICAL MODELS WITH THE DATA OF SELECTED SUBSTORM INTERVALS S.B. Lunyushkin1, O.I. Bemgardt1, V.V. Mishin', V.M. Mishin1, D.Sh. Shirapov2 1 Institute o f Solar-Terrestrial Physics SB RAS, Irkutsk, Russia, e-mail: lunyushkin@iszf.irk.ru 2East Siberia State University o f Technology and Management, Ulan-Ude, Russia Abstract. Large-scale maps of the electric potential distribution in the disturbed polar ionosphere during the relatively weak 26 February 2008 substorm obtained by two different methods, are compared with each other. One series of the electric potential maps has been derived on the basis of SuperDARN measurement data, another set maps has been calculated by the magnetogram inversion technique. We also compare graphs of variation o f the cross polar cap potential drop during the considered substorm, obtained by the two methods. The SuperDARN maps are founded to mainly describe the regular, whereas the MIT maps - both regular and irregular components of the spatial electric potential distribution. Introduction Electric fields and currents in the high-latitude regions of the Earth’s ionosphere are the most important components of the coupled magnetosphere-ionosphere (M-I) system. These ionospheric electric fields and currents are largely driven by magnetospheric electric fields and currents, which are in turn driven by interactions between the magnetosphere and the solar wind. These interactions occur via reconnection between the interplanetary magnetic field (IMF) and the dayside geomagnetic field and by means of the quasi-viscous mechanism in magnetospheric boundary layers. Based on the dependence of high-latitude electric fields on the IMF and solar wind parameters or geomagnetic conditions, a number of statistical or empirical models of large-scale electric potential distributions in the polar ionosphere has been derived from the measurement data by the DMSP and DE-2 satellites and SuperDARN radars [Papitashvili and Rich, 2002; Ruohoniemi and Greenwald, 2005; Weimer, 2005; Cousins and Shepherd, 2010]. Along with the well-known system of large-scale plasma convection vortices and electric currents in the M-I system, researchers have become aware of formation of mesoscale cells during substorms, each of which involves a plasma vortex and a field-aligned current (FAC) [ Kauristie et al., 2000; Shi et al., 2012; Mishin et al., 2013]. Also, in recent years, studies of the mesoscale and large-scale variability in the high-latitude ionospheric convection have been initiated on the basis of the SuperDARN measurement data [Cousins et al., 2013]. In this paper, we analyze the observed dynamics of the electric potential distributions in the polar ionosphere from the data on the 26 February 2008 substorms. The time series of the electric potential distributions (2D maps) were calculated by using the magnetogram inversion technique (MIT-ISTP) [Mishin et al., 1979; Mishin, 1990; Mishin et al., 2000]. These MIT data calculated for the specified instants are compared with the similar data obtained from statistical results of measurements with SuperDARN radars. Data We use the above MIT, the results of measuring the plasma and IMF parameters onboard spacecraft WIND (http://omniweb.gsfc.nasa.gov) , the AE indices that we obtained from 42 ground-based magnetic stations at the geomagnetic latitudes Ф > 40°, and the above statistical model for the electric potential distribution in the ionosphere derived from SuperDARN measurement data ( http://vt.superdarn.org/tiki-index.php) . The MIT input data are three components of the variable magnetic field vector measured by the network comprising 110 ground- based magnetometers in the northern hemisphere at Ф > 40° (see references in Acknowledgements). The main MIT output data are: three types of 2D distribution maps of the equivalent ionospheric current density, the electric potential (U), the FAC density, and Joule heating power released in the polar ionosphere (Q,). The maps are calculated each minute on a fixed'grid with grid size MLat x MLong = Г x 10°. On the basis of 2D distribution maps of the FAC density, the polar cap boundary is determined as the R1 high-latitude boundary, by which we calculate the open magnetic flux (XP1) through the polar cap and the Poynting flux into the magnetosphere, e' = const-(4,i)2-VSw [Mishin et al, 1992; Mishin et al., 2000]. We use our own spatially inhomogeneous and variable in time model for the corpuscular electric conductivities of the polar ionosphere [Shirapov et al., 2000]. Fig. lb shows that during the addressed 02-06 UT interval of the 26 February 2008 events, the solar wind dynamic pressure (Pd) varies with a small amplitude around the mean, comparatively low and quasi-constant 1 5 nPa level. The pre-onset phase of the first observed disturbance cycle is initiated near 02:45 UT by the IMF В southward turn up to the — 1.5 nT level (Fig. la). The AE index (Fig. lc) growth starts near 02:50 UT from an extremely low level < 10 nT. Further, one observes a slow, almost monotonous, growth in AE to an increased but *P hysics o f Auroral Phenom ena", Proc. XXXVIII A nnual Sem inar , A patity, pp. 20-23, 2 0 1 5 © Kola Science Centre, Russian Academy of Science, 2015 Polar Geophysical Institute 20