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.

А Pig. 10. A schematic illustration for- the progressive disruption of the nightside westward tail current during m a gne tospheric substorm (Nagai, 1982). С (Coleman and McPherron,1970), but the recent multi-satellite observation of the distant magnetic field enabled us to know the longitudinal extent and the progressive widening of the region of tail-current disruption (Kokubun and McPherron,1981j Hagai,1982; Barfield et al.,1985), as illustrated in Fig. 10. The production of the current-system shown in Fig.10, i.e., the disrup tion of the tail current, is regarded also as an appearance of a partial ring current, which consists of a pair of field-aligned currents in a n a rrow longi tude range near the midnight meridian connected with a westward electric current in the ionosphere and an eastward current in the equatorial plane of the magnetosphere (which cancels the westward ring current in the m a g n e t o sphere). This partial ring current-system on the night side of the earth does not influence at all the amount of antisunward current in the earth's environ mental space detectable from the MAGSAT data analysis, because this partial ring current-system at the substorm onset does not include any net sunward or antisunward electric current in the ionosphere below the MAGSAT orbit of the dawn-dusk meridian. If we launch ei low-altitude satellite with its orbital plane nearly in the sun-earth direction, the disruption of the tail current must be observed by such a satellite, because the disrupted tail current 1з converted to a net dawn-dusk electric current in the ionosphere bel o w the satellite orbit. SOME REMARKS FOR THE FUTURE STUDY OF EXTERNAL ELECTRIC CURRENTS BASED ON THE EXPERIENCE OF MAGSAT PROJECT. MAGSAT made an excellent contribution to the study of electric currents in the earth's environmental space, especially those flowing in the ionosphere because of its low altitude in comparison with other previous satellites for magnetic field measurements. However the MAGSAT paths are only in the dawn and dusk meridians, in order to avoid a possible contamination from an intense electric current in the sunlit hemisphere of the earth. In the future it will be necessary to launch some low-altitude satellites, which measure the magnetic field possibly along all local-time meridians over the earth. Such satellites will contribute to solving the folio wing important questions: 1) the local-time range of the region where the east-west toroidal magne field is observed near the dip equator; 84