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.

on the dayoide, while it is influenced by the magnetotail on the downstream side of the solar wind. It has been reported that a sudden change in the magnetic field configuration (from a tail-like field to a dipolar field) takes place at the level of synchronous satellites at the onset of magnetic substorm, which accompanies a sudden change in the spatial pattern of electric currents around the earth. This paper summarizes the recent knowledge on the electric currents flowing in the magnetosphere-ionosphere (including field-aligned currents in the polar regions) known mainly from the analysis of magnetic field data observed by MAGSAT and some synchronous-orbit satellites. FIELD-ALIGNED CURRENTS IN HIGH LATITUDES. The first experimental detec tion of field-aligned currents was reported by Zmuda et al. (1966) in their observation of magnetic field by 1963 38C satellite at u height of 1100 km over the auroral zone, although the authors attributed the observed result to transverse hydromagnetic w a v e s . The principal satellites contributed to the study of field-aligned currents before 1979 were AZUR (Theile and Praetorius, 1973) at 400-3000 km altitude, 0G0-2, 4, and 6 satellites (Langel, 1974a,b) at 400-550 km height, and TRIAD (Iijima and Potemra, 1976a) at 800 k m altitude. Before the launching of IJAGSAT, the spatial pattern of incoming and outflowing field-aligned currents was roughly known as shown by Pig.1. The MAGSAT data enabled us to know the fine structure of field-aligned current pattern near the dawn and dusk meridians (Hughes et al.,1982; Iijima et al.,1982; Wallis et al.,1982; Zanetti and Potemra,1982; Zanetti et al.,1962). An example of the result of such a study is given in Fig.2. Fig. 1. Spatial distribution and flow directions of large-scale field- aligned currents during v/eakly disturbed conditions from TRIAD satelli+«„ (Iijima and Potemra, 1976b). 12 SB Cuztents Into 0 lonotphexe .ЕЭ Cuizents fnom lonospkeze 6 76