Структура и динамика полярных токовых систем : материалы международного симпозиума «Полярные геомагнитные явления», 25-31 мая, Суздаль, СССР / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Апатиты : [б. и.], 1988.

T.V.Kozelova, L.L.Lazutin, M.I.Pudovkin, A.Pedersen, K.-H.Glassmeier THE ELECTRIC FIELD IN THE MAGNETOSPHERE IH THE VICINITY OF THE WESTERN EDGE OF THE SUBSTORM CURRENT WEDGE ABSTRACT. The analysis of the electric field behaviour at 6.6 Rg shows that the change of the direction of the azimuthal component of the quasi- stationary electric field is connected with the fronts of proton fluXes with energies > 20 keV. The observed picture of the E^ field agrees with the polar ization fields on tho pressure gradients in the magnetosphere. The correspon ding FACs promote creation or intensification of the three-dimensional subetorm current system, INTRODUCTION. It is well known that during the magnetospheric substorm active phase the initial disturbance is localised both along the latitude and longitude; with time it expands in all directions. Field-aligned currents (FACs) are flowing both on the astern and western edges of the disturbed regions, but the most prominent (and, perhaps, most important) substorm manifestations for all types of observations occur on the western edge where the upward FAC j,*, is located. The change of the magnetic field from tailward to a more dipolar configuration and sharp increasings of energetic electron fluxes in a large energy range are the well established features of the sub storm at a distance of 6.6 R^ but the accompanying behaviour of the electric field is not studied sufficiently. For example, intense (up to 20 mV/m) but short living (~ 10 s), E-field increases have been detected by the geostation ary satellite GEOS-2 and the authors /1/ consider them to be connected with the localized FACs during the substorm. Besides, in the midnight sector at 6.6 Rg near the equatorial plane more prolonged E-field enhancements (up to 10 mV/m) with the sunward and dawn-dusk components are observed (south-western directions in the projection on the ionosphere) /2/. In several cases the electric field of this direction was registered when the supposed GE0S-2 foot print was located inside the westward travelling surge (WTS) /3,4/. At the same time it follows from the referred papers that the behaviour of the E-field during the substorm is much more complicated; in particular, the azimuthal component sometimes may be directed eastward, whereas the meridional one may become tailward (the northward direction in projection to the ionosphere). We will analyze E-field GEOS-2 data together with simultaneous measure ments of energetic particles for the periods when satellite was located near the westward edge of the substorm current wedge, where a large-scale upward field-aligned current j* is located. Conjugate Scandinavian geophysical observations and data of Soviet stations have been used for the detailed diagnosis of active phase development. To eliminate possible errors in con jugation only large-scale WTS ( > 1 0 km) have been chosen with additional 35