Электродинамические процессы в высоких широтах: материалы междунарордного симпозиума «Полярные геомагнитные явления», 25-31 мая 1986 г., Суздаль, СССР / Междунар. геодез. и геофиз. союз, Междунар. ассоц. геомагнетизма и аэрономии ; Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т ; [редкол.: О. М. Распопов (отв. ред.). и др.]. - Апатиты : Кольский филиал АН СССР, 1988.

P.E.SANDHOLT, A.EGELAND, C.S.DEEHR, V.G.VOROBJEV, G.V.STARKOV, V.L.ZVEREV, Ya.I.FELDSTEIN DAYSIDE AURORAL LUMINOSITY IN RELATION TO THE IMP AND MAGNETOSPHERIC SUBSTORM ACTIVITY x. INTRODUCTION. Dynamical processes governing the particle, momentum and energy transfer from the solar wind to the magnetosphere and upper atmosph ere are the main topics of solar-terrestrial research. Questions concerning the dynamics of the plasma sheet of the nightside magnetosphere and its interaction with the auroral aone ionosphere have been studied i n some detail (e.g. Akasofu,1977; Shepherd et al.,1980). In recent years attention has been focused on the physics of the dayside magnetospheric boundary layers (e.g.Paschmann,19S4; E astman,1984) and the coupling to the dayside polar ionosphere (e.g.Holtet and Egeland (eds.),1985). It has been speculated for a long time that the solar wind plasma can penetrate into the magnetosphere through magnetic neutral regions resulting from the coupling between the solar wind and the earth's magnetic field. The first indication of the existence of a pair of magnetic neutral points (or lines) at high latitudes on the dayside magnetopause was provided by Chapman and Ferraro (1931), in a theoretical discussion of the interaction between a conducting plasma and the geomagnetic field. The first direct evidence for plasma entry in these regions was obtained around 1970 when satellite observations revealed the existence of plasmas of magnetosheath origin at low altitudes (Heikkila and W i nningham,1971) and at higher altitu des in the dayside magnetosphere (Frank,1971). During the International Geophysical Year 1957/58 ground-based auroral observations at polar stations showed auroral emissions to exist at magne tic midday (Feldstein and Starkov,1967). Spectroscopic and photometric observations of these emissions were made by Yevlashin (1961) and Eather and Mende (1971), who showed that the spectroscopic rations 1(01 630.0 run)/ 1(01 557.7 nm) and 1(01 630.0 r m O / K N g 427.8 nm) are enhanced by a n order of magnitude relative to the typical midnight emissions. Now there is a strong evidence that the midday polar cusp emissions are consequences of the penetration into the magnetosphere and the subsequ ent precipitation of magnetosheath plasma (e.g.Holtet and Egeland (eds), 1985). Thus, the polar cusp aurora is a "footpront" of plasma entry from the solar wind. These emissions can then be used as a diagnostic tool in the study of electrodynamic coupling between the shocked solar wind and the earth's magnetosphere and upper atmosphere. Ground observations allow continuous monitoring of the auroral emis sions. Due to the inaccessibility of the polar regions which satisfy the observation conditions, i.e. correct distance to the geomagnetic pole and so far north in geographic latitude that the sunlight does not disturb the II6