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.

The present wo r k describes the pattern of the morphological and spectral characteristics of auroras in the dayside sector of auroral oval and their relationships to the IMP parameters and to magnetic activity level. W e do not aim at relating these characteristics to the sources in the magnetosphere and to the processes occuring at the magnetopause, but rather try to present the most comprehensive pattern of the events observed in the dayside auroras. Figure 13 shows the pattern sunmarizing the results of studying the auroral luminosity in the dayside sector. The pattern has been constructed for a m e a n level of magnetic activity. The dotted lines are the boundaries of the oval of discrete auroral forms. The arrow indicate the mo t i o n directions of the discrete auroral forms. The pattern illustrates the mutual position of the auroral luminosity regions w i t h different spectral parameters. The dots in the n e a r-noon sector indicate the region of relatively soft precipitation where the *630.0^*557.7 ratio i s >;> 1 * The daytime rayed arcs are formed at the equatorward boundary of the region, whereupon they move polewards. In the p renoon sector, the equatorward side of the region borders the zone where the Ig 3 0 0 / I 5 5 7 7 ratio is •« 1. At early dawn hours the homogeneous auroral arcs m oving equatorwards are embedded in the diffuse luminosity zone. In the after* noon sector, the auroral luminosity is concentrated mainly inside the auroral oval and the ^ 6 3 0 . 0 ^ 5 5 7 . 7 r a ^° 'there ia 1. In this region the directions of the meridional m otions of auroras are changed, i.e. the daytime rayed auroral arcs mov i n g polewards are replaced b y the dusk-sector homogeneous arcs mov i n g equatorwards. The pattern i n Figure 13 does not include the discrete auroral gap. The gap was found b y Dandekar a n d Pike (1978) and is regarded as a permanent feature of the dayside sector of the oval (Dandekar,1979; Me n g and L u n d i n , 1986). The ezistence of the discrete auroral g a p whose position is centered at 1000 M L T was found f r o m the photographs taken on board the DMSP series of satellites. Because, however, of a relativel y low sensitivity of the equip ment and a strong background the ga p m a y be rather a consequence of a rapid decrease in the aurora intensity than an overlap of the discrete forms across the no o n sector. The gap is rarely observed b y the ground-based all-sky cameras. I n Pig.9, for example, the discrete auroral forms occur continuously 12 M iT 138