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.

throughout the observation period including the near-noon sector. The occurrences of the discrete auroral gapa in the near-noon sector of the oval were studied in detail by Vorobjev and Rezhanov (19Ѳ2) using the ascafilms from Pyramids and Svalbard. Only 14 occurrences of the gap in the 0830-1130 MLT interval were observed during the entire IGY period. The gaps were observed at AE < 1 0 0 nT during the periods of minimum variations of mag netic field in the polar oap. Patchy auroras and individual raya were observ ved in the gap region. The width and the latitudinal position of the gap were-found (cf.Dandekar,1979) to depend on the IMP B z-component. To discriminate between the effects of the IMP B z component and of the magnetic activity on the position of daytime auroras one must use the periods when one of the two parameters varies relatively little. Figure (a,b,c) shows the dependence of the variations in the position of the dayside aurora equatorward boundary on the value of the B s-component for three events chara cterized by different, but approximately constant throughout the examined intervals, levels of magnetic activity which were 0.3 and 5 as regards the Q-index. The magnetio activity level was found on the basis of the magneto- grams from station Churchill located in the midnight sector of the auroral ?one. In the examined events the position of the equatorward boundary of the auroral zone was compared after each 5-min interval to the respective values of the IMP В -component. The dashed lines correspond to the linear regression equivalent obtained by the least squares method. The values of the correla tion coefficient "r" and the standard deviation 6 are indicated. A distinct dependence of the position of the dayside aurora boundary on the B z-component can be seen despite a relatively small range of B a variations in the exami ned events. On the other hand, an overall shift of the regression line to ф' a 0I.I2.I978. V ь 13.I2.I979. ф 1 с 05.01.19*1. Figure 14. The position of the daytime aurora equatorward boundary v ersus the IMF В-component value for three Individual events (a)-(c) and for the entire data set (d). The same data a re also shown in the лФ1 , В coordinates (e), ЛФ 1 is the deviation of the auroral гопе equatorward boundary from the boundary of the me a n statistical oval defined according to Starkov (1969)s Q is magnetic activity index, “r" is correlation г coefficient, 0 is standard deviation. 139